2031:
the capacity in terms of the number of simultaneous users is limited. There are a fixed number of orthogonal codes, time slots or frequency bands that can be allocated for CDM, TDMA, and FDMA systems, which remain underutilized due to the bursty nature of telephony and packetized data transmissions. There is no strict limit to the number of users that can be supported in an asynchronous CDMA system, only a practical limit governed by the desired bit error probability since the SIR (signal-to-interference ratio) varies inversely with the number of users. In a bursty traffic environment like mobile telephony, the advantage afforded by asynchronous CDMA is that the performance (bit error rate) is allowed to fluctuate randomly, with an average value determined by the number of users times the percentage of utilization. Suppose there are 2
2093:
this was military applications including guidance and communication systems. These systems were designed using spread spectrum because of its security and resistance to jamming. Asynchronous CDMA has some level of privacy built in because the signal is spread using a pseudo-random code; this code makes the spread-spectrum signals appear random or have noise-like properties. A receiver cannot demodulate this transmission without knowledge of the pseudo-random sequence used to encode the data. CDMA is also resistant to jamming. A jamming signal only has a finite amount of power available to jam the signal. The jammer can either spread its energy over the entire bandwidth of the signal or jam only part of the entire signal.
2437:
445:
2139:
despreading operations. The new collaborative multi-user receiver consists of two stages: group multi-user detection (MUD) stage to suppress the MAI between the groups and a low-complexity maximum-likelihood detection stage to recover jointly the co-spread users' data using minimal
Euclidean-distance measure and users' channel-gain coefficients. An enhanced CDMA version known as interleave-division multiple access (IDMA) uses the orthogonal interleaving as the only means of user separation in place of signature sequence used in CDMA system.
436:" national civil mobile phone service for cars, based on the Soviet MRT-1327 standard. The phone system weighed 11 kg (24 lb). It was placed in the trunk of the vehicles of high-ranking officials and used a standard handset in the passenger compartment. The main developers of the Altai system were VNIIS (Voronezh Science Research Institute of Communications) and GSPI (State Specialized Project Institute). In 1963 this service started in Moscow, and in 1970 Altai service was used in 30 USSR cities.
1993:
these systems. This is not true for asynchronous CDMA; rejection of unwanted signals is only partial. If any or all of the unwanted signals are much stronger than the desired signal, they will overwhelm it. This leads to a general requirement in any asynchronous CDMA system to approximately match the various signal power levels as seen at the receiver. In CDMA cellular, the base station uses a fast closed-loop power-control scheme to tightly control each mobile's transmit power.
1558:
53:
805:
2121:
cells do not interfere with each other. In a CDMA system, the same frequency can be used in every cell, because channelization is done using the pseudo-random codes. Reusing the same frequency in every cell eliminates the need for frequency planning in a CDMA system; however, planning of the different pseudo-random sequences must be done to ensure that the received signal from one cell does not correlate with the signal from a nearby cell.
2110:
multipath channel induces at least one chip of delay, the multipath signals will arrive at the receiver such that they are shifted in time by at least one chip from the intended signal. The correlation properties of the pseudo-random codes are such that this slight delay causes the multipath to appear uncorrelated with the intended signal, and it is thus ignored.
2117:, which exploits multipath delay components to improve the performance of the system. A rake receiver combines the information from several correlators, each one tuned to a different path delay, producing a stronger version of the signal than a simple receiver with a single correlation tuned to the path delay of the strongest signal.
1257:
1538:
1396:
1104:
350:
In these schemes, the message is modulated on a longer spreading sequence, consisting of several chips (0es and 1es). Due to their very advantageous auto- and crosscorrelation characteristics, these spreading sequences have also been used for radar applications for many decades, where they are called
2083:
time slots. Furthermore, it would require significant overhead to continually allocate and deallocate the orthogonal-code, time-slot or frequency-channel resources. By comparison, asynchronous CDMA transmitters simply send when they have something to say and go off the air when they do not, keeping
1992:
Since each user generates MAI, controlling the signal strength is an important issue with CDMA transmitters. A CDM (synchronous CDMA), TDMA, or FDMA receiver can in theory completely reject arbitrarily strong signals using different codes, time slots or frequency channels due to the orthogonality of
1864:
Further, after decoding, all values greater than 0 are interpreted as 1, while all values less than zero are interpreted as 0. For example, after decoding, data0 is (2, −2, 2, 2), but the receiver interprets this as (1, 0, 1, 1). Values of exactly 0 mean that the sender did not transmit any data, as
825:
An analogy to the problem of multiple access is a room (channel) in which people wish to talk to each other simultaneously. To avoid confusion, people could take turns speaking (time division), speak at different pitches (frequency division), or speak in different languages (code division). CDMA is
431:
in Moscow made an experimental model of a wearable automatic mobile phone, called LK-1 by him, with a base station. LK-1 has a weight of 3 kg, 20–30 km operating distance, and 20–30 hours of battery life. The base station, as described by the author, could serve several customers. In 1958,
2133:
A novel collaborative multi-user transmission and detection scheme called collaborative CDMA has been investigated for the uplink that exploits the differences between users' fading channel signatures to increase the user capacity well beyond the spreading length in the MAI-limited environment. The
2120:
Frequency reuse is the ability to reuse the same radio channel frequency at other cell sites within a cellular system. In the FDMA and TDMA systems, frequency planning is an important consideration. The frequencies used in different cells must be planned carefully to ensure signals from different
2092:
Most modulation schemes try to minimize the bandwidth of this signal since bandwidth is a limited resource. However, spread-spectrum techniques use a transmission bandwidth that is several orders of magnitude greater than the minimum required signal bandwidth. One of the initial reasons for doing
2062:
In other words, asynchronous CDMA is ideally suited to a mobile network where large numbers of transmitters each generate a relatively small amount of traffic at irregular intervals. CDM (synchronous CDMA), TDMA, and FDMA systems cannot recover the underutilized resources inherent to bursty traffic
1543:
Each user in synchronous CDMA uses a code orthogonal to the others' codes to modulate their signal. An example of 4 mutually orthogonal digital signals is shown in the figure below. Orthogonal codes have a cross-correlation equal to zero; in other words, they do not interfere with each other. In
2124:
Since adjacent cells use the same frequencies, CDMA systems have the ability to perform soft hand-offs. Soft hand-offs allow the mobile telephone to communicate simultaneously with two or more cells. The best signal quality is selected until the hand-off is complete. This is different from hard
2109:
Another reason CDMA is resistant to multipath interference is because the delayed versions of the transmitted pseudo-random codes will have poor correlation with the original pseudo-random code, and will thus appear as another user, which is ignored at the receiver. In other words, as long as the
2105:
can be used to assist in recovering this lost data. CDMA signals are also resistant to multipath fading. Since the spread-spectrum signal occupies a large bandwidth, only a small portion of this will undergo fading due to multipath at any given time. Like the narrow-band interference, this will
2030:
Asynchronous CDMA offers a key advantage in the flexible allocation of resources i.e. allocation of spreading sequences to active users. In the case of CDM (synchronous CDMA), TDMA, and FDMA the number of simultaneous orthogonal codes, time slots, and frequency slots respectively are fixed, hence
1959:
When mobile-to-base links cannot be precisely coordinated, particularly due to the mobility of the handsets, a different approach is required. Since it is not mathematically possible to create signature sequences that are both orthogonal for arbitrarily random starting points and which make full
817:
the received signal with the locally generated code of the desired user. If the signal matches the desired user's code, then the correlation function will be high and the system can extract that signal. If the desired user's code has nothing in common with the signal, the correlation should be as
1996:
In 2019, schemes to precisely estimate the required length of the codes in dependence of
Doppler and delay characteristics have been developed. Soon after, machine learning based techniques that generate sequences of a desired length and spreading properties have been published as well. These are
1964:
CDMA systems. A spreading sequence is a binary sequence that appears random but can be reproduced in a deterministic manner by intended receivers. These spreading sequences are used to encode and decode a user's signal in asynchronous CDMA in the same manner as the orthogonal codes in synchronous
1977:
are an example of a spreading sequence suitable for this purpose, as there is low correlation between the codes. If all of the users are received with the same power level, then the variance (e.g., the noise power) of the MAI increases in direct proportion to the number of users. In other words,
812:
Each user in a CDMA system uses a different code to modulate their signal. Choosing the codes used to modulate the signal is very important in the performance of CDMA systems. The best performance occurs when there is good separation between the signal of a desired user and the signals of other
1719:
Now, due to physical properties of interference, if two signals at a point are in phase, they add to give twice the amplitude of each signal, but if they are out of phase, they subtract and give a signal that is the difference of the amplitudes. Digitally, this behaviour can be modelled by the
2138:
performance in flat fading channels, which is a major research challenge for overloaded CDMA systems. In this approach, instead of using one sequence per user as in conventional CDMA, the authors group a small number of users to share the same spreading sequence and enable group spreading and
2014:
TDMA systems must carefully synchronize the transmission times of all the users to ensure that they are received in the correct time slot and do not cause interference. Since this cannot be perfectly controlled in a mobile environment, each time slot must have a guard time, which reduces the
1790:
This raw signal is called an interference pattern. The receiver then extracts an intelligible signal for any known sender by combining the sender's code with the interference pattern. The following table explains how this works and shows that the signals do not interfere with one another:
1988:
to allow receivers to partially discriminate against unwanted signals. Signals encoded with the specified spreading sequences are received, while signals with different sequences (or the same sequences but different timing offsets) appear as wideband noise reduced by the spreading factor.
2125:
hand-offs utilized in other cellular systems. In a hard-hand-off situation, as the mobile telephone approaches a hand-off, signal strength may vary abruptly. In contrast, CDMA systems use the soft hand-off, which is undetectable and provides a more reliable and higher-quality signal.
1548:
are used to encode the signal to separate different users. Since each of the 64 Walsh codes is orthogonal to all other, the signals are channelized into 64 orthogonal signals. The following example demonstrates how each user's signal can be encoded and decoded.
1110:
841:
The digital modulation method is analogous to those used in simple radio transceivers. In the analog case, a low-frequency data signal is time-multiplied with a high-frequency pure sine-wave carrier and transmitted. This is effectively a frequency convolution
1402:
1263:
971:
432:
Kupriyanovich made the new experimental "pocket" model of mobile phone. This phone weighed 0.5 kg. To serve more customers, Kupriyanovich proposed the device, which he called "correlator." In 1958, the USSR also started the development of the "
2010:
In theory CDMA, TDMA and FDMA have exactly the same spectral efficiency, but, in practice, each has its own challenges – power control in the case of CDMA, timing in the case of TDMA, and frequency generation/filtering in the case of FDMA.
2516:
M. Mazzella, M. Cohen, D. Rouffet, M. Louie and K. S. Gilhousen, "Multiple access techniques and spectrum utilisation of the GLOBALSTAR mobile satellite system," Fourth IEE Conference on
Telecommunications 1993, Manchester, UK, 1993, pp.
2096:
CDMA can also effectively reject narrow-band interference. Since narrow-band interference affects only a small portion of the spread-spectrum signal, it can easily be removed through notch filtering without much loss of information.
822:. If the code is correlated with the signal at any time offset other than zero, the correlation should be as close to zero as possible. This is referred to as auto-correlation and is used to reject multi-path interference.
427:. It was shown that through the use of linear methods, there are three types of signal separation: frequency, time and compensatory. The technology of CDMA was used in 1957, when the young military radio engineer
2733:
394:
In the US, one of the earliest descriptions of CDMA can be found in the summary report of
Project Hartwell on "The Security of Overseas Transport", which was a summer research project carried out at the
2435:, Куприянович (Leonid Kupriyanovich), "Устройства вызова и коммутации каналов радиотелефонной связи (Devices for calling and switching radio communication channels)", published 1957-11-04
347:
for example or as a permanent pilot/signalling channel to allow users to synchronize their local oscillators to a common system frequency, thereby also estimating the channel parameters permanently.
1941:
When the receiver attempts to decode the signal using sender1's code, the data is all zeros; therefore the cross-correlation is equal to zero and it is clear that sender1 did not transmit any data.
525:
in the frequency domain, unlike other narrow pulse codes. In CDMA a locally generated code runs at a much higher rate than the data to be transmitted. Data for transmission is combined by bitwise
1252:{\displaystyle \mathbf {a} \cdot (-\mathbf {a} +\mathbf {b} )=-\|\mathbf {a} \|^{2},\ {\text{since}}\ {-\mathbf {a} }\cdot \mathbf {a} +\mathbf {a} \cdot \mathbf {b} =-\|\mathbf {a} \|^{2}+0,}
963:
1723:
If sender0 has code (1, −1) and data (1, 0, 1, 1), and sender1 has code (1, 1) and data (0, 0, 1, 1), and both senders transmit simultaneously, then this table describes the coding steps:
830:
and rejected. Similarly, in radio CDMA, each group of users is given a shared code. Many codes occupy the same channel, but only users associated with a particular code can communicate.
370:(OFDM), which typically makes it very robust and efficient (and equipping them with accurate ranging capabilities, which is difficult without CDMA). Other schemes use subcarriers based on
1533:{\displaystyle \mathbf {b} \cdot (\mathbf {a} -\mathbf {b} )=-\|\mathbf {b} \|^{2},\ {\text{since}}\ \mathbf {b} \cdot \mathbf {a} -\mathbf {b} \cdot \mathbf {b} =0-\|\mathbf {b} \|^{2}.}
850:. These are binary square waves that form a complete orthonormal set. The data signal is also binary and the time multiplication is achieved with a simple XOR function. This is usually a
1391:{\displaystyle \mathbf {b} \cdot (\mathbf {a} +\mathbf {b} )=\|\mathbf {b} \|^{2},\ {\text{since}}\ \mathbf {b} \cdot \mathbf {a} +\mathbf {b} \cdot \mathbf {b} =0+\|\mathbf {b} \|^{2},}
1099:{\displaystyle \mathbf {a} \cdot (\mathbf {a} +\mathbf {b} )=\|\mathbf {a} \|^{2},\ {\text{since}}\ \mathbf {a} \cdot \mathbf {a} +\mathbf {a} \cdot \mathbf {b} =\|\mathbf {a} \|^{2}+0,}
1978:
unlike synchronous CDMA, the signals of other users will appear as noise to the signal of interest and interfere slightly with the desired signal in proportion to number of users.
517:
CDMA is a spread-spectrum multiple-access technique. A spread-spectrum technique spreads the bandwidth of the data uniformly for the same transmitted power. A spreading code is a
2022:
of the signal spectrum because of user mobility. The guard bands will reduce the probability that adjacent channels will interfere, but decrease the utilization of the spectrum.
358:
For space-based communication applications, CDMA has been used for many decades due to the large path loss and
Doppler shift caused by satellite motion. CDMA is often used with
801:
is called the spreading factor or processing gain and determines to a certain extent the upper limit of the total number of users supported simultaneously by a base station.
799:
703:
668:
286:, where several transmitters can send information simultaneously over a single communication channel. This allows several users to share a band of frequencies (see
757:
730:
581:
554:
1997:
highly competitive with the classic Gold and Welch sequences. These are not generated by linear-feedback-shift-registers, but have to be stored in lookup tables.
613:
633:
3363:
3330:
3353:
1965:
CDMA (shown in the example above). These spreading sequences are statistically uncorrelated, and the sum of a large number of spreading sequences results in
1569:. (Although mutual orthogonality is the only condition, these vectors are usually constructed for ease of decoding, for example columns or rows from
3103:
2705:
1573:.) An example of orthogonal functions is shown in the adjacent picture. These vectors will be assigned to individual users and are called the
254:
3183:
3146:
297:
CDMA optimizes the use of available bandwidth as it transmits over the entire frequency range and does not limit the user's frequency range.
3188:
2954:
3231:
2908:
2559:
529:(exclusive OR) with the faster code. The figure shows how a spread-spectrum signal is generated. The data signal with pulse duration of
201:
367:
3469:
2528:
826:
analogous to the last example where people speaking the same language can understand each other, but other languages are perceived as
336:) shut down 3G CDMA-based networks in 2022 and 2024, rendering handsets supporting only those protocols unusable for calls, even to
324:
carriers, also uses "wideband CDMA", or W-CDMA, as well as TD-CDMA and TD-SCDMA, as its radio technologies. Many carriers (such as
3348:
2432:
3464:
2396:
2238:
3490:
3065:
846:) of the two signals, resulting in a carrier with narrow sidebands. In the digital case, the sinusoidal carrier is replaced by
378:
and enable a larger gap between the virtual center frequency and the subcarriers, which is not the case for OFDM subcarriers.
3259:
2681:
396:
150:
3096:
2237:
systems. This relates to the properties of the CDMA technology: all users operate in the same frequency range that impacts
2169:
2159:
1868:
Assume signal0 = (1, −1, −1, 1, 1, −1, 1, −1) is transmitted alone. The following table shows the decode at the receiver:
181:
3163:
2734:"A comparison study of the uplink performance of W-CDMA and OFDM for mobile multimedia communications via LEO satellites"
2357:
2180:
833:
In general, CDMA belongs to two basic categories: synchronous (orthogonal codes) and asynchronous (pseudorandom codes).
3500:
3133:
329:
247:
140:
932:
3368:
3226:
2903:
2851:
2607:
2573:
2542:
404:
186:
3378:
2067:
codes, time slots or frequency channels that can be assigned to individual transmitters. For instance, if there are
3158:
371:
130:
759:, the bandwidth of the spread-spectrum signal is much larger than the bandwidth of the original signal. The ratio
3340:
3302:
3221:
3141:
3089:
2845:
2327:
1960:
use of the code space, unique "pseudo-random" or "pseudo-noise" sequences called spreading sequences are used in
1950:
1625:) = (1, −1) and the data that the user wishes to transmit is (1, 0, 1, 1), then the transmitted symbols would be
433:
363:
191:
126:
85:
2102:
3241:
2935:
2777:
135:
1782:
Because signal0 and signal1 are transmitted at the same time into the air, they add to produce the raw signal
3505:
3358:
3274:
3175:
2217:
584:
287:
240:
206:
3039:
518:
3456:
3373:
2306:
843:
30:
This article is about a channel access method. For the mobile phone technology referred to as CDMA, see
121:
95:
3437:
2930:
2599:
457:
424:
362:(BPSK) in its simplest form, but can be combined with any modulation scheme like (in advanced cases)
359:
3432:
2966:
2699:
2149:
456:
Synchronous CDM (code-division 'multiplexing', an early generation of CDMA) was implemented in the
444:
333:
161:
3081:
2503:
2018:
Similarly, FDMA systems must use a guard band between adjacent channels, due to the unpredictable
2751:
Talk at
Princeton Institute for Advanced Study on Solomon Golomb's work on pseudorandom sequences
762:
60:
2821:
2047:
users that talk all of the time. The key difference here is that the bit error probability for
3442:
3008:
408:
301:
3495:
3427:
3116:
3112:
2857:
2593:
1970:
673:
638:
283:
275:
228:
223:
2755:
3411:
3018:
2992:
2898:
2098:
1954:
735:
708:
559:
532:
428:
145:
75:
70:
17:
1716:
chosen from that set, but the construction method of the transmitted vector is identical.
8:
3151:
2826:
1786:(1, −1, −1, 1, 1, −1, 1, −1) + (−1, −1, −1, −1, 1, 1, 1, 1) = (0, −2, −2, 0, 2, 0, 2, 0).
590:
325:
2950:
2770:
2687:
2489:
2175:
2134:
authors show that it is possible to achieve this increase at a low complexity and high
618:
522:
3310:
2666:
Proceedings of the 2019 International
Technical Meeting of the Institute of Navigation
3406:
3320:
3124:
3055:
2677:
2661:
2603:
2569:
2565:
2538:
2534:
2417:
Ageev, D. V. (1935). "Bases of the Theory of Linear
Selection. Code Demultiplexing".
2186:
869:
is represented by the vector (1, 0, 1, 1). Vectors can be multiplied by taking their
862:
819:
814:
106:
2719:
Shakya, Indu L. (2011). "High User
Capacity Collaborative CDMA". IET Communications.
2691:
294:
technology and a special coding scheme (where each transmitter is assigned a code).
3393:
3293:
3023:
2669:
2366:
1985:
176:
90:
80:
2816:
2392:
2005:
2801:
2786:
2191:
1982:
375:
291:
2075:
users that talk half of the time, then half of the time there will be more than
818:
close to zero as possible (thus eliminating the signal); this is referred to as
2589:
2352:
2135:
2019:
847:
2370:
2015:
probability that users will interfere, but decreases the spectral efficiency.
482:, known as CDMA2000, is used by several mobile phone companies, including the
386:
The technology of code-division multiple access channels has long been known.
3484:
3034:
2924:
2763:
2451:
2114:
1566:
858:
400:
290:). To permit this without undue interference between the users, CDMA employs
2750:
3029:
2961:
2863:
2233:
The UMTS networks and other CDMA based systems are also known as a kind of
1570:
917:
to each other. Some properties of the dot product aid understanding of how
851:
526:
461:
449:
420:
44:
2307:"AT&T is shutting down its 3G network. Here's how it could impact you"
1557:
873:, by summing the products of their respective components (for example, if
3013:
2732:
Papathanassiou, A., Salkintzis, A. K., & Mathiopoulos, P. T. (2001).
2084:
the same signature sequence as long as they are connected to the system.
1579:
870:
352:
2673:
2598:. Translated by von Schmoeger, Hedwig Jourdan (First English ed.).
2000:
423:(USSR), the first work devoted to this subject was published in 1935 by
3401:
3060:
2064:
1545:
483:
52:
1969:(MAI) that is approximated by a Gaussian noise process (following the
1705:
For the purposes of this article, we call this constructed vector the
27:
Channel access method used by various radio communication technologies
3383:
2945:
1974:
804:
556:(symbol period) is XORed with the code signal with pulse duration of
505:
2419:
Proceedings of the
Leningrad Experimental Institute of Communication
3315:
3216:
3111:
3070:
2987:
2978:
2893:
2662:"Pure Pilot Signals: How short can we choose GNSS spreading codes?"
2154:
1588:. In the interest of brevity, the rest of this example uses codes
468:
343:
It can be also used as a channel or medium access technology, like
313:
35:
2659:
2431:
3211:
2972:
2940:
2888:
2164:
479:
305:
31:
836:
3249:
3206:
2883:
2196:
2006:
Efficient practical utilization of the fixed frequency spectrum
918:
913:). If the dot product is zero, the two vectors are said to be
494:
1720:
addition of the transmission vectors, component by component.
865:
representing the data strings. For example, the binary string
3325:
2785:
2629:
Digital Communications: Fundamentals and Applications, 2nd ed
2582:
827:
472:
399:
from June to August 1950. Further research in the context of
344:
337:
279:
196:
635:= bit time.) Therefore, the bandwidth of the data signal is
2270:
Principles of Spread-Spectrum Communication Systems, 4th ed
2221:
2051:
users talking all of the time is constant, whereas it is a
490:
317:
2087:
355:(with a very short sequence length of typically 8 to 32).
2561:
Radio Network Planning and Optimisation for UMTS (Vol. 2)
2311:
2106:
result in only a small loss of data and can be overcome.
1910:
decode0 = ((1, −1), (−1, 1), (1, −1), (1, −1)) · (1, −1)
1599:. A 1 bit is represented by transmitting a positive code
321:
2592:; Seidenberg, Peter; Althoff, Marc Peter (March 2003) .
1913:
decode1 = ((1, −1), (−1, 1), (1, −1), (1, −1)) · (1, 1)
1757:
encode1 = 2(0, 0, 1, 1) − (1, 1, 1, 1) = (−1, −1, 1, 1)
1888:
code0 = (1, −1), signal = (1, −1, −1, 1, 1, −1, 1, −1)
1833:
decode0 = ((0, −2), (−2, 0), (2, 0), (2, 0)) · (1, −1)
1754:
encode0 = 2(1, 0, 1, 1) − (1, 1, 1, 1) = (1, −1, 1, 1)
309:
2588:
1891:
code1 = (1, 1), signal = (1, −1, −1, 1, 1, −1, 1, −1)
1836:
decode1 = ((0, −2), (−2, 0), (2, 0), (2, 0)) · (1, 1)
2384:
2328:"Verizon will shutter its 3G CDMA by the end of 2022"
2001:
Advantages of asynchronous CDMA over other techniques
1811:
code0 = (1, −1), signal = (0, −2, −2, 0, 2, 0, 2, 0)
1405:
1266:
1113:
974:
935:
857:
Synchronous CDMA exploits mathematical properties of
765:
738:
711:
676:
641:
621:
593:
562:
535:
460:(GPS). This predates and is distinct from its use in
1814:
code1 = (1, 1), signal = (0, −2, −2, 0, 2, 0, 2, 0)
2344:
2025:
1595:Each user is associated with a different code, say
1561:
An example of 4 mutually orthogonal digital signals
670:and the bandwidth of the spread spectrum signal is
2557:
1532:
1390:
1251:
1098:
957:
793:
751:
724:
697:
662:
627:
607:
575:
548:
282:communication technologies. CDMA is an example of
2558:Laiho, J.; Wacker, A.; Novosad, T., eds. (2002).
2350:
3482:
2224:combining with satellite multiple beam antennas.
1924:decode1 = ((1 − 1), (−1 + 1), (1 − 1), (1 − 1))
1921:decode0 = ((1 + 1), (−1 − 1), (1 + 1), (1 + 1))
1847:decode1 = ((0 − 2), (−2 + 0), (2 + 0), (2 + 0))
1844:decode0 = ((0 + 2), (−2 + 0), (2 + 0), (2 + 0))
1603:, and a 0 bit is represented by a negative code
958:{\displaystyle \mathbf {a} \cdot \mathbf {b} =0}
813:users. The separation of the signals is made by
2353:"The Origins of Spread-Spectrum Communications"
1879:
1876:
1873:
1802:
1799:
1796:
1734:
1731:
1728:
1565:Start with a set of vectors that are mutually
316:, are often simply referred to as "CDMA", but
3097:
2771:
2035:users that only talk half of the time, then 2
837:Code-division multiplexing (synchronous CDMA)
248:
2704:: CS1 maint: multiple names: authors list (
2526:
2390:
2305:Kelly, Samantha Murphy (February 22, 2022).
1932:data0 = (2, −2, 2, 2), meaning (1, 0, 1, 1)
1518:
1509:
1448:
1439:
1376:
1367:
1306:
1297:
1231:
1222:
1159:
1150:
1078:
1069:
1014:
1005:
2660:Enneking, Antreich, Appel, Almeida (2019).
1858:data1=(−2, −2, 2, 2), meaning (0, 0, 1, 1)
1712:Each sender has a different, unique vector
512:
3104:
3090:
2778:
2764:
2292:Principles of Mobile Communication, 4th ed
2241:and, hence, reduces coverage and capacity.
1855:data0=(2, −2, 2, 2), meaning (1, 0, 1, 1)
368:orthogonal frequency-division multiplexing
255:
241:
2640:
2638:
2627:Sklar, Bernard; Ray, Pabitra K. (2014).
2626:
2622:
2620:
2267:
2039:users can be accommodated with the same
1556:
803:
443:
300:It is used as the access method in many
2644:
2614:(NB. Based on the 2001 German edition.)
2397:Engineering and Technology History Wiki
2325:
2285:
2283:
2281:
2279:
2263:
2261:
2259:
2257:
2088:Spread-spectrum characteristics of CDMA
374:(BOC modulation), which is inspired by
14:
3483:
2718:
2530:WCDMA for UMTS: HSPA Evolution and LTE
2289:
1935:data1 = (0, 0, 0, 0), meaning no data
1743:code0 = (1, −1), data0 = (1, 0, 1, 1)
3085:
2759:
2635:
2617:
2527:Holma, H.; Toskala, A., eds. (2007).
2416:
2304:
2128:
1746:code1 = (1, 1), data1 = (0, 0, 1, 1)
521:in the time domain that has a narrow
493:3G mobile phone standard, which uses
397:Massachusetts Institute of Technology
2807:Code-division multiple access (CDMA)
2276:
2254:
2170:Orthogonal variable spreading factor
2160:Comparison of mobile phone standards
1944:
504:satellite system for transportation
2358:IEEE Transactions on Communications
2181:Quadrature-division multiple access
2055:quantity (with the same mean) for 2
24:
2726:
2216:Globalstar uses elements of CDMA,
25:
3517:
2852:Frequency-hopping spread spectrum
2744:
2393:"Oral-History: Claude E. Shannon"
2183:(QDMA), an implementation of CDMA
2172:(OVSF), an implementation of CDMA
2071:time slots in a TDMA system and 2
1701:) = (1, −1, −1, 1, 1, −1, 1, −1).
308:, also called "cdmaOne", and its
2059:users talking half of the time.
2026:Flexible allocation of resources
1513:
1496:
1488:
1480:
1472:
1443:
1426:
1418:
1407:
1371:
1354:
1346:
1338:
1330:
1301:
1287:
1279:
1268:
1226:
1212:
1204:
1196:
1187:
1154:
1137:
1129:
1115:
1073:
1062:
1054:
1046:
1038:
1009:
995:
987:
976:
945:
937:
389:
372:binary offset carrier modulation
51:
2846:Direct-sequence spread spectrum
2712:
2653:
2647:Wireless Communications, 2nd ed
2551:
2520:
2510:
2496:
2482:
2470:
2458:
2326:Johnson, Allison (2021-03-30).
2227:
2210:
2079:users needing to use more than
1951:Direct-sequence spread spectrum
1776:= (−1, −1, −1, −1, 1, 1, 1, 1)
1769:= (1, −1, −1, 1, 1, −1, 1, −1)
414:
364:quadrature amplitude modulation
2444:
2425:
2410:
2351:Robert A. Scholtz (May 1982).
2319:
2298:
1430:
1414:
1291:
1275:
1141:
1122:
999:
983:
13:
1:
3491:Code division multiple access
3421:Delay and disruption tolerant
2391:Robert Price (28 July 1982).
2248:
268:Code-division multiple access
3040:Low probability of intercept
3009:PN (pseudorandom noise) code
2864:Time-hopping spread spectrum
2738:IEEE Personal Communications
2504:"First Russian Mobile Phone"
1967:multiple access interference
7:
2142:
2063:due to the fixed number of
808:Generation of a CDMA signal
794:{\displaystyle T_{b}/T_{c}}
407:was carried out in 1952 at
10:
3522:
2600:John Wiley & Sons, Ltd
2290:Stuber, Gordon L. (2017).
1981:All forms of CDMA use the
1948:
1902:decode1 = pattern.vector1
1899:decode0 = pattern.vector0
1865:in the following example:
1825:decode1 = pattern.vector1
1822:decode0 = pattern.vector0
1761:
1750:
1739:
1552:
1544:the case of IS-95, 64-bit
897:), then their dot product
500:CDMA has been used in the
381:
320:, the 3G standard used by
29:
3501:Radio resource management
3455:
3420:
3392:
3339:
3301:
3292:
3273:
3258:
3240:
3197:
3174:
3132:
3123:
3048:
3001:
2917:
2873:
2835:
2794:
2789:in digital communications
2645:Molisch, Andreas (2010).
2371:10.1109/TCOM.1982.1095547
2043:bit error probability as
1774:= (−1, −1, 1, 1) ⊗ (1, 1)
1772:signal1 = encode1 ⊗ code1
1767:= (1, −1, 1, 1) ⊗ (1, −1)
1765:signal0 = encode0 ⊗ code0
458:Global Positioning System
360:binary phase-shift keying
3066:Statistical multiplexing
2203:
2150:CDMA spectral efficiency
2113:Some CDMA devices use a
854:mixer in the circuitry.
513:Steps in CDMA modulation
162:Statistical multiplexing
844:Wiener–Khinchin theorem
698:{\displaystyle 1/T_{c}}
663:{\displaystyle 1/T_{b}}
439:
3443:Dynamic Source Routing
3113:Channel access methods
3024:Power spectral density
2595:UMTS: The Fundamentals
2268:Torrieri, Don (2018).
1562:
1534:
1392:
1253:
1100:
959:
809:
795:
753:
726:
699:
664:
629:
609:
583:(chip period). (Note:
577:
550:
478:The Qualcomm standard
475:, marketed as cdmaOne.
452:
302:mobile phone standards
224:Channel access methods
3056:Digital communication
2918:Major implementations
2858:Chirp spread spectrum
2566:John Wiley & Sons
2535:John Wiley & Sons
2506:. September 18, 2006.
1971:central limit theorem
1560:
1535:
1393:
1254:
1101:
960:
929:are orthogonal, then
807:
796:
754:
752:{\displaystyle T_{b}}
732:is much smaller than
727:
725:{\displaystyle T_{c}}
700:
665:
630:
610:
578:
576:{\displaystyle T_{c}}
551:
549:{\displaystyle T_{b}}
447:
276:channel access method
229:Medium access control
3506:Media access control
3117:media access control
2668:. pp. 925–935.
2235:interference-limited
2099:Convolution encoding
1592:with only two bits.
1403:
1264:
1111:
972:
933:
763:
736:
709:
674:
639:
619:
591:
560:
533:
429:Leonid Kupriyanovich
165:(variable bandwidth)
110:(constant bandwidth)
3341:Collision avoidance
2674:10.33012/2019.16737
2433:Soviet Union 115494
1607:. For example, if
608:{\displaystyle 1/T}
587:is proportional to
3303:Collision recovery
2602:. pp. 18–19.
2590:Walke, Bernhard H.
2493:2, 1959, p. 18–19.
2490:Tekhnika Molodezhi
2467:7, 1957, p. 43–44.
2176:Pseudorandom noise
2129:Collaborative CDMA
1707:transmitted vector
1563:
1530:
1388:
1249:
1096:
955:
921:works. If vectors
810:
791:
749:
722:
695:
660:
625:
605:
573:
546:
523:ambiguity function
519:pseudo-random code
453:
3478:
3477:
3457:Duplexing methods
3451:
3450:
3288:
3287:
3079:
3078:
2683:978-0-936406-21-3
2187:Rise over thermal
1973:in statistics).
1945:Asynchronous CDMA
1939:
1938:
1862:
1861:
1780:
1779:
1470:
1466:
1462:
1328:
1324:
1320:
1181:
1177:
1173:
1036:
1032:
1028:
820:cross-correlation
628:{\displaystyle T}
265:
264:
61:Analog modulation
16:(Redirected from
3513:
3299:
3298:
3130:
3129:
3106:
3099:
3092:
3083:
3082:
3019:Near–far problem
2836:Spread spectrum
2780:
2773:
2766:
2757:
2756:
2721:
2720:
2716:
2710:
2709:
2703:
2695:
2657:
2651:
2650:
2642:
2633:
2632:
2624:
2615:
2613:
2586:
2580:
2579:
2555:
2549:
2548:
2524:
2518:
2514:
2508:
2507:
2500:
2494:
2486:
2480:
2479:10, 1958, p. 66.
2474:
2468:
2462:
2456:
2448:
2442:
2441:
2440:
2436:
2429:
2423:
2422:
2414:
2408:
2407:
2405:
2403:
2388:
2382:
2381:
2379:
2377:
2348:
2342:
2341:
2339:
2338:
2323:
2317:
2316:
2302:
2296:
2295:
2287:
2274:
2273:
2265:
2242:
2231:
2225:
2214:
1986:spreading factor
1955:near–far problem
1871:
1870:
1794:
1793:
1726:
1725:
1539:
1537:
1536:
1531:
1526:
1525:
1516:
1499:
1491:
1483:
1475:
1468:
1467:
1464:
1460:
1456:
1455:
1446:
1429:
1421:
1410:
1397:
1395:
1394:
1389:
1384:
1383:
1374:
1357:
1349:
1341:
1333:
1326:
1325:
1322:
1318:
1314:
1313:
1304:
1290:
1282:
1271:
1258:
1256:
1255:
1250:
1239:
1238:
1229:
1215:
1207:
1199:
1191:
1190:
1179:
1178:
1175:
1171:
1167:
1166:
1157:
1140:
1132:
1118:
1105:
1103:
1102:
1097:
1086:
1085:
1076:
1065:
1057:
1049:
1041:
1034:
1033:
1030:
1026:
1022:
1021:
1012:
998:
990:
979:
964:
962:
961:
956:
948:
940:
800:
798:
797:
792:
790:
789:
780:
775:
774:
758:
756:
755:
750:
748:
747:
731:
729:
728:
723:
721:
720:
704:
702:
701:
696:
694:
693:
684:
669:
667:
666:
661:
659:
658:
649:
634:
632:
631:
626:
614:
612:
611:
606:
601:
582:
580:
579:
574:
572:
571:
555:
553:
552:
547:
545:
544:
376:Manchester codes
278:used by various
257:
250:
243:
177:Packet switching
166:
111:
55:
41:
40:
21:
3521:
3520:
3516:
3515:
3514:
3512:
3511:
3510:
3481:
3480:
3479:
3474:
3447:
3416:
3388:
3335:
3284:
3269:
3254:
3236:
3193:
3170:
3119:
3110:
3080:
3075:
3044:
2997:
2951:Cordless phones
2913:
2869:
2831:
2802:Spread spectrum
2790:
2787:Spread spectrum
2784:
2747:
2729:
2727:Further reading
2724:
2717:
2713:
2700:cite conference
2697:
2696:
2684:
2658:
2654:
2643:
2636:
2625:
2618:
2610:
2587:
2583:
2576:
2568:. p. 303.
2556:
2552:
2545:
2525:
2521:
2515:
2511:
2502:
2501:
2497:
2487:
2483:
2475:
2471:
2463:
2459:
2455:8, 1957, p. 49.
2449:
2445:
2438:
2430:
2426:
2415:
2411:
2401:
2399:
2389:
2385:
2375:
2373:
2349:
2345:
2336:
2334:
2324:
2320:
2303:
2299:
2288:
2277:
2266:
2255:
2251:
2246:
2245:
2232:
2228:
2215:
2211:
2206:
2201:
2192:Spread spectrum
2145:
2131:
2090:
2028:
2008:
2003:
1983:spread-spectrum
1957:
1947:
1880:Decode sender1
1877:Decode sender0
1803:Decode sender1
1800:Decode sender0
1775:
1773:
1768:
1766:
1735:Encode sender1
1732:Encode sender0
1700:
1693:
1686:
1679:
1672:
1665:
1658:
1651:
1624:
1617:
1555:
1521:
1517:
1512:
1495:
1487:
1479:
1471:
1463:
1451:
1447:
1442:
1425:
1417:
1406:
1404:
1401:
1400:
1379:
1375:
1370:
1353:
1345:
1337:
1329:
1321:
1309:
1305:
1300:
1286:
1278:
1267:
1265:
1262:
1261:
1234:
1230:
1225:
1211:
1203:
1195:
1186:
1182:
1174:
1162:
1158:
1153:
1136:
1128:
1114:
1112:
1109:
1108:
1081:
1077:
1072:
1061:
1053:
1045:
1037:
1029:
1017:
1013:
1008:
994:
986:
975:
973:
970:
969:
944:
936:
934:
931:
930:
848:Walsh functions
839:
785:
781:
776:
770:
766:
764:
761:
760:
743:
739:
737:
734:
733:
716:
712:
710:
707:
706:
689:
685:
680:
675:
672:
671:
654:
650:
645:
640:
637:
636:
620:
617:
616:
597:
592:
589:
588:
567:
563:
561:
558:
557:
540:
536:
534:
531:
530:
515:
442:
417:
392:
384:
292:spread spectrum
284:multiple access
261:
211:
168:
164:
163:
155:
113:
109:
108:
100:
39:
28:
23:
22:
15:
12:
11:
5:
3519:
3509:
3508:
3503:
3498:
3493:
3476:
3475:
3473:
3472:
3467:
3461:
3459:
3453:
3452:
3449:
3448:
3446:
3445:
3440:
3435:
3430:
3424:
3422:
3418:
3417:
3415:
3414:
3409:
3404:
3398:
3396:
3394:Collision-free
3390:
3389:
3387:
3386:
3381:
3376:
3371:
3366:
3361:
3356:
3351:
3345:
3343:
3337:
3336:
3334:
3333:
3328:
3323:
3318:
3313:
3307:
3305:
3296:
3290:
3289:
3286:
3285:
3283:
3282:
3279:
3277:
3271:
3270:
3268:
3267:
3264:
3262:
3256:
3255:
3253:
3252:
3246:
3244:
3238:
3237:
3235:
3234:
3229:
3224:
3219:
3214:
3209:
3203:
3201:
3195:
3194:
3192:
3191:
3186:
3180:
3178:
3172:
3171:
3169:
3168:
3167:
3166:
3156:
3155:
3154:
3149:
3138:
3136:
3127:
3121:
3120:
3109:
3108:
3101:
3094:
3086:
3077:
3076:
3074:
3073:
3068:
3063:
3058:
3053:
3049:
3046:
3045:
3043:
3042:
3037:
3032:
3027:
3021:
3016:
3011:
3005:
3003:
3002:Major concepts
2999:
2998:
2996:
2995:
2990:
2985:
2982:
2976:
2970:
2964:
2958:
2957:
2948:
2943:
2938:
2933:
2928:
2921:
2919:
2915:
2914:
2912:
2911:
2906:
2901:
2896:
2891:
2886:
2880:
2878:
2871:
2870:
2868:
2867:
2861:
2855:
2849:
2842:
2840:
2833:
2832:
2830:
2829:
2824:
2822:Commercial use
2819:
2814:
2810:
2809:
2804:
2798:
2796:
2792:
2791:
2783:
2782:
2775:
2768:
2760:
2754:
2753:
2746:
2745:External links
2743:
2742:
2741:
2740:, 8(3), 35–43.
2728:
2725:
2723:
2722:
2711:
2682:
2652:
2634:
2616:
2608:
2581:
2574:
2550:
2543:
2519:
2509:
2495:
2481:
2469:
2457:
2443:
2424:
2409:
2383:
2365:(5): 822–854.
2343:
2318:
2297:
2275:
2252:
2250:
2247:
2244:
2243:
2226:
2208:
2207:
2205:
2202:
2200:
2199:
2194:
2189:
2184:
2178:
2173:
2167:
2162:
2157:
2152:
2146:
2144:
2141:
2136:bit error rate
2130:
2127:
2089:
2086:
2027:
2024:
2007:
2004:
2002:
1999:
1946:
1943:
1937:
1936:
1933:
1930:
1926:
1925:
1922:
1919:
1915:
1914:
1911:
1908:
1904:
1903:
1900:
1897:
1893:
1892:
1889:
1886:
1882:
1881:
1878:
1875:
1860:
1859:
1856:
1853:
1849:
1848:
1845:
1842:
1838:
1837:
1834:
1831:
1827:
1826:
1823:
1820:
1816:
1815:
1812:
1809:
1805:
1804:
1801:
1798:
1788:
1787:
1778:
1777:
1770:
1763:
1759:
1758:
1755:
1752:
1748:
1747:
1744:
1741:
1737:
1736:
1733:
1730:
1703:
1702:
1698:
1691:
1684:
1677:
1670:
1663:
1656:
1649:
1622:
1615:
1571:Walsh matrices
1554:
1551:
1541:
1540:
1529:
1524:
1520:
1515:
1511:
1508:
1505:
1502:
1498:
1494:
1490:
1486:
1482:
1478:
1474:
1459:
1454:
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1445:
1441:
1438:
1435:
1432:
1428:
1424:
1420:
1416:
1413:
1409:
1398:
1387:
1382:
1378:
1373:
1369:
1366:
1363:
1360:
1356:
1352:
1348:
1344:
1340:
1336:
1332:
1317:
1312:
1308:
1303:
1299:
1296:
1293:
1289:
1285:
1281:
1277:
1274:
1270:
1259:
1248:
1245:
1242:
1237:
1233:
1228:
1224:
1221:
1218:
1214:
1210:
1206:
1202:
1198:
1194:
1189:
1185:
1170:
1165:
1161:
1156:
1152:
1149:
1146:
1143:
1139:
1135:
1131:
1127:
1124:
1121:
1117:
1106:
1095:
1092:
1089:
1084:
1080:
1075:
1071:
1068:
1064:
1060:
1056:
1052:
1048:
1044:
1040:
1025:
1020:
1016:
1011:
1007:
1004:
1001:
997:
993:
989:
985:
982:
978:
954:
951:
947:
943:
939:
838:
835:
788:
784:
779:
773:
769:
746:
742:
719:
715:
692:
688:
683:
679:
657:
653:
648:
644:
624:
604:
600:
596:
570:
566:
543:
539:
514:
511:
510:
509:
498:
487:
476:
465:
441:
438:
416:
413:
391:
388:
383:
380:
263:
262:
260:
259:
252:
245:
237:
234:
233:
232:
231:
226:
218:
217:
216:Related topics
213:
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169:
160:
157:
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105:
102:
101:
99:
98:
93:
88:
83:
78:
73:
67:
64:
63:
57:
56:
48:
47:
26:
9:
6:
4:
3:
2:
3518:
3507:
3504:
3502:
3499:
3497:
3494:
3492:
3489:
3488:
3486:
3471:
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3346:
3344:
3342:
3338:
3332:
3329:
3327:
3324:
3322:
3319:
3317:
3316:Slotted ALOHA
3314:
3312:
3309:
3308:
3306:
3304:
3300:
3297:
3295:
3291:
3281:
3280:
3278:
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3257:
3251:
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3173:
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3150:
3148:
3145:
3144:
3143:
3140:
3139:
3137:
3135:
3131:
3128:
3126:
3125:Channel-based
3122:
3118:
3114:
3107:
3102:
3100:
3095:
3093:
3088:
3087:
3084:
3072:
3069:
3067:
3064:
3062:
3059:
3057:
3054:
3051:
3050:
3047:
3041:
3038:
3036:
3035:Rake receiver
3033:
3031:
3028:
3025:
3022:
3020:
3017:
3015:
3012:
3010:
3007:
3006:
3004:
3000:
2994:
2991:
2989:
2986:
2983:
2981:(aka IS-2000)
2980:
2977:
2975:(aka cdmaOne)
2974:
2971:
2968:
2965:
2963:
2960:
2959:
2956:
2952:
2949:
2947:
2944:
2942:
2939:
2937:
2934:
2932:
2929:
2926:
2925:Space Network
2923:
2922:
2920:
2916:
2910:
2907:
2905:
2902:
2900:
2897:
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2892:
2890:
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2823:
2820:
2818:
2815:
2812:
2811:
2808:
2805:
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2800:
2799:
2797:
2795:Main articles
2793:
2788:
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2776:
2774:
2769:
2767:
2762:
2761:
2758:
2752:
2749:
2748:
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2667:
2663:
2656:
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2641:
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2630:
2623:
2621:
2611:
2609:0-470-84557-0
2605:
2601:
2597:
2596:
2591:
2585:
2577:
2575:9780470031391
2571:
2567:
2563:
2562:
2554:
2546:
2544:9781119991908
2540:
2536:
2532:
2531:
2523:
2513:
2505:
2499:
2492:
2491:
2485:
2478:
2477:Nauka i Zhizn
2473:
2466:
2465:Yuniy technik
2461:
2454:
2453:
2452:Nauka i Zhizn
2447:
2434:
2428:
2420:
2413:
2398:
2394:
2387:
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2240:
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2195:
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2174:
2171:
2168:
2166:
2163:
2161:
2158:
2156:
2153:
2151:
2148:
2147:
2140:
2137:
2126:
2122:
2118:
2116:
2115:rake receiver
2111:
2107:
2104:
2100:
2094:
2085:
2082:
2078:
2074:
2070:
2066:
2060:
2058:
2054:
2050:
2046:
2042:
2038:
2034:
2023:
2021:
2020:Doppler shift
2016:
2012:
1998:
1994:
1990:
1987:
1984:
1979:
1976:
1972:
1968:
1963:
1956:
1952:
1942:
1934:
1931:
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1598:
1593:
1591:
1587:
1586:chipping code
1583:
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1522:
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1503:
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1235:
1219:
1216:
1208:
1200:
1192:
1183:
1168:
1163:
1147:
1144:
1133:
1125:
1119:
1107:
1093:
1090:
1087:
1082:
1066:
1058:
1050:
1042:
1023:
1018:
1002:
991:
980:
968:
967:
966:
952:
949:
941:
928:
924:
920:
916:
912:
908:
904:
900:
896:
892:
888:
884:
880:
876:
872:
868:
864:
860:
859:orthogonality
855:
853:
849:
845:
834:
831:
829:
823:
821:
816:
806:
802:
786:
782:
777:
771:
767:
744:
740:
717:
713:
690:
686:
681:
677:
655:
651:
646:
642:
622:
602:
598:
594:
586:
568:
564:
541:
537:
528:
524:
520:
507:
503:
499:
496:
492:
488:
485:
481:
477:
474:
470:
466:
463:
462:mobile phones
459:
455:
454:
451:
446:
437:
435:
430:
426:
422:
412:
410:
406:
402:
398:
390:United States
387:
379:
377:
373:
369:
365:
361:
356:
354:
348:
346:
341:
339:
335:
331:
327:
323:
319:
315:
311:
307:
303:
298:
295:
293:
289:
285:
281:
277:
273:
269:
258:
253:
251:
246:
244:
239:
238:
236:
235:
230:
227:
225:
222:
221:
220:
219:
215:
214:
208:
205:
203:
200:
198:
195:
193:
190:
188:
185:
183:
180:
178:
175:
174:
172:
171:
167:
159:
158:
152:
149:
147:
144:
142:
139:
137:
134:
132:
128:
125:
123:
120:
119:
117:
116:
112:
104:
103:
97:
94:
92:
89:
87:
84:
82:
79:
77:
74:
72:
69:
68:
66:
65:
62:
59:
58:
54:
50:
49:
46:
43:
42:
37:
33:
19:
3496:Multiplexing
3294:Packet-based
3198:
3030:Process gain
2875:
2837:
2806:
2737:
2714:
2665:
2655:
2646:
2628:
2594:
2584:
2564:. New York:
2560:
2553:
2529:
2522:
2512:
2498:
2488:
2484:
2476:
2472:
2464:
2460:
2450:
2446:
2427:
2418:
2412:
2400:. Retrieved
2386:
2374:. Retrieved
2362:
2356:
2346:
2335:. Retrieved
2331:
2321:
2310:
2300:
2291:
2269:
2234:
2229:
2212:
2132:
2123:
2119:
2112:
2108:
2103:interleaving
2095:
2091:
2080:
2076:
2072:
2068:
2061:
2056:
2052:
2048:
2044:
2040:
2036:
2032:
2029:
2017:
2013:
2009:
1995:
1991:
1980:
1966:
1962:asynchronous
1961:
1958:
1940:
1867:
1863:
1789:
1781:
1722:
1718:
1713:
1711:
1706:
1704:
1695:
1688:
1681:
1674:
1667:
1660:
1653:
1646:
1642:
1638:
1634:
1630:
1619:
1612:
1608:
1604:
1600:
1596:
1594:
1589:
1585:
1578:
1574:
1564:
1542:
926:
922:
914:
910:
906:
902:
898:
894:
890:
886:
882:
878:
874:
866:
856:
852:Gilbert cell
840:
832:
824:
811:
516:
501:
450:mobile phone
425:Dmitry Ageev
421:Soviet Union
418:
415:Soviet Union
405:anti-jamming
393:
385:
357:
353:Barker codes
349:
342:
299:
296:
271:
267:
266:
182:Dynamic TDMA
141:Polarization
129: /
107:Circuit mode
45:Multiplexing
2817:Hedy Lamarr
1546:Walsh codes
871:dot product
815:correlating
448:A CDMA2000
409:Lincoln Lab
3485:Categories
3402:Token Ring
3061:Modulation
2402:30 January
2376:30 January
2337:2021-10-09
2249:References
2065:orthogonal
1975:Gold codes
1949:See also:
1567:orthogonal
915:orthogonal
484:Globalstar
330:UScellular
312:evolution
3407:Token bus
3384:CSMA/CARP
2946:Bluetooth
2332:The Verge
1519:‖
1510:‖
1507:−
1493:⋅
1485:−
1477:⋅
1449:‖
1440:‖
1437:−
1423:−
1412:⋅
1377:‖
1368:‖
1351:⋅
1335:⋅
1307:‖
1298:‖
1273:⋅
1232:‖
1223:‖
1220:−
1209:⋅
1193:⋅
1184:−
1160:‖
1151:‖
1148:−
1126:−
1120:⋅
1079:‖
1070:‖
1059:⋅
1043:⋅
1015:‖
1006:‖
981:⋅
942:⋅
705:. Since
585:bandwidth
506:logistics
502:OmniTRACS
471:standard
366:(QAM) or
288:bandwidth
3412:MS-ALOHA
3217:TD-SCDMA
3071:Waveform
3052:See also
2988:Qualcomm
2979:CDMA2000
2962:Cellular
2894:TD-SCDMA
2692:86666944
2517:306-311.
2155:CDMA2000
2143:See also
861:between
615:, where
486:network.
469:Qualcomm
326:AT&T
314:CDMA2000
36:CDMA2000
3364:CSMA/CA
3331:CSMA/CD
3321:R-ALOHA
3250:HC-SDMA
3232:MC-CDMA
3227:FH-CDMA
3222:DS-CDMA
3212:TD-CDMA
3184:MF-TDMA
3152:SC-FDMA
2993:Verizon
2941:GLONASS
2936:Galileo
2909:MC-CDMA
2904:FH-CDMA
2899:DS-CDMA
2889:TD-CDMA
2876:schemes
2838:methods
2827:More...
2813:History
2421:: 3–35.
2165:cdmaOne
2041:average
1553:Example
863:vectors
480:IS-2000
419:In the
401:jamming
382:History
334:Verizon
274:) is a
146:Spatial
32:cdmaOne
3207:W-CDMA
2969:Mobile
2927:(NASA)
2884:W-CDMA
2866:(THSS)
2854:(FHSS)
2848:(DSSS)
2690:
2680:
2606:
2572:
2541:
2439:
2197:W-CDMA
2053:random
1469:
1461:
1327:
1319:
1180:
1172:
1035:
1027:
919:W-CDMA
885:) and
495:W-CDMA
202:SC-FDM
3433:VANET
3428:MANET
3354:MACAW
3326:AX.25
3311:ALOHA
3189:STDMA
3147:OFDMA
3026:(PSD)
2973:IS-95
2967:EV-DO
2874:CDMA
2860:(CSS)
2688:S2CID
2204:Notes
1874:Step
1797:Step
1729:Step
1645:) = (
1584:, or
1465:since
1323:since
1176:since
1031:since
965:and:
828:noise
473:IS-95
434:Altai
345:ALOHA
306:IS-95
280:radio
207:MC-SS
197:OFDMA
3359:CSMA
3349:MACA
3275:PAMA
3260:PDMA
3242:SDMA
3199:CDMA
3176:TDMA
3164:WDMA
3134:FDMA
3115:and
3014:Chip
2984:Also
2955:DECT
2706:link
2678:ISBN
2604:ISBN
2570:ISBN
2539:ISBN
2404:2022
2378:2022
2239:SINR
2222:FDMA
2220:and
2218:TDMA
2101:and
1953:and
1582:code
1580:chip
1575:code
925:and
867:1011
491:UMTS
489:The
467:The
440:Uses
403:and
332:and
318:UMTS
272:CDMA
192:DSSS
187:FHSS
136:SDMA
34:and
18:CDMA
3470:FDD
3465:TDD
3438:DTN
3379:HCF
3374:PCF
3369:DCF
3159:WDM
3142:FDM
2931:GPS
2670:doi
2367:doi
2312:CNN
1666:, −
1659:, −
1611:= (
889:= (
877:= (
527:XOR
338:911
322:GSM
151:OAM
131:WDM
127:FDM
122:TDM
96:SSB
86:QAM
3487::
2953::
2736:.
2702:}}
2698:{{
2686:.
2676:.
2664:.
2637:^
2619:^
2537:.
2533:.
2395:.
2363:30
2361:.
2355:.
2330:.
2309:.
2278:^
2256:^
1929:4
1918:3
1907:2
1896:1
1885:0
1852:4
1841:3
1830:2
1819:1
1808:0
1762:2
1751:1
1740:0
1709:.
1694:,
1687:,
1680:,
1673:,
1652:,
1641:,
1637:,
1635:−v
1633:,
1618:,
1605:−v
1577:,
911:bd
909:+
907:ac
905:=
893:,
881:,
411:.
340:.
328:,
310:3G
304:.
91:SM
81:PM
76:FM
71:AM
3105:e
3098:t
3091:v
2779:e
2772:t
2765:v
2708:)
2694:.
2672::
2649:.
2631:.
2612:.
2578:.
2547:.
2406:.
2380:.
2369::
2340:.
2315:.
2294:.
2272:.
2081:N
2077:N
2073:N
2069:N
2057:N
2049:N
2045:N
2037:N
2033:N
1714:v
1699:1
1696:v
1692:0
1689:v
1685:1
1682:v
1678:0
1675:v
1671:1
1668:v
1664:0
1661:v
1657:1
1654:v
1650:0
1647:v
1643:v
1639:v
1631:v
1629:(
1623:1
1620:v
1616:0
1613:v
1609:v
1601:v
1597:v
1590:v
1528:.
1523:2
1514:b
1504:0
1501:=
1497:b
1489:b
1481:a
1473:b
1458:,
1453:2
1444:b
1434:=
1431:)
1427:b
1419:a
1415:(
1408:b
1386:,
1381:2
1372:b
1365:+
1362:0
1359:=
1355:b
1347:b
1343:+
1339:a
1331:b
1316:,
1311:2
1302:b
1295:=
1292:)
1288:b
1284:+
1280:a
1276:(
1269:b
1247:,
1244:0
1241:+
1236:2
1227:a
1217:=
1213:b
1205:a
1201:+
1197:a
1188:a
1169:,
1164:2
1155:a
1145:=
1142:)
1138:b
1134:+
1130:a
1123:(
1116:a
1094:,
1091:0
1088:+
1083:2
1074:a
1067:=
1063:b
1055:a
1051:+
1047:a
1039:a
1024:,
1019:2
1010:a
1003:=
1000:)
996:b
992:+
988:a
984:(
977:a
953:0
950:=
946:b
938:a
927:b
923:a
903:v
901:·
899:u
895:d
891:c
887:v
883:b
879:a
875:u
842:(
787:c
783:T
778:/
772:b
768:T
745:b
741:T
718:c
714:T
691:c
687:T
682:/
678:1
656:b
652:T
647:/
643:1
623:T
603:T
599:/
595:1
569:c
565:T
542:b
538:T
508:.
497:.
464:.
270:(
256:e
249:t
242:v
38:.
20:)
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