in dsss the signal is recovered using

The spreading code used in this example was only four bits long. The physical layer provides three levels of functionality. DSSS basics     Direct sequence spread spectrum requires the overall channel (including, where relevant, equalisation in the receiver) to have approximately unity gain, pure delay characteristics over the whole signal bandwidth. Synchronization is achieved in 802.11 by sending the essential parameters—dwell time, frequency sequence number, and present channel number—in a frequency parameter set field that is part of a beacon transmission sent periodically on the channel. This is multiplied with the spreading code to regenerate the original data. Frequency modulation     In the receiver the received signal is XORed with the PN stream to recover the original data stream; this is equivalent to correlation with the known PN sequence. The MAC layer uses this field to determine the end of a PPDU frame. Figure 18.12. In signal processing, a signal is a function that conveys information about a phenomenon. Here is the protocol on both the sender and receiver side. In the given example, the spread signal of the user A at the code A, and diffused signal … The resulting data stream has a higher data rate than the data itself. Radio Signals     The symbol rate (data rate) for the DSSS signals is 1.0 MHz, and there are 11 chips per symbol, which means the chip rate is 11.0 MHz. In Europe 13 frequencies are allowed between 2.412 and 2.472 GHz. A cooperative receiver with the knowledge … Normal DSSS decoding compares the signal to expected values, using a correlation algorithm that multiplies the two and gives a score. The DS-CDMA has been used in commercial applications of mobile communications. In this case, the synthesizer is being sequentially programmed with different frequencies by the PN sequence to modulate the desired signal over a much wider frequency band. ▶︎ Check our Supplier Directory. To decode the signal and receive the original data, the CDMA signal is first demodulated from the carrier to reconstitute the high speed data stream. The CRC field contains the results of a calculated frame check sequence from the sending station. 3. A DSSS signal looks like noise if you don’t know the patterns to look for. The PLCP preamble and PLCP header are always transmitted at 1 Mbps, and the MPDU can be sent at 1 or 2 Mbps. Table 6.1. For 1 Mbps data rate, nominal frequency deviation is ± 160 kHz. Morse Telegraph Key History & Development. With this channel arrangement, a user can configure multiple DSSS networks to operate simultaneously in the same area. Spectrum of a Bluetooth waveform at fc−4 MHz, Figure 3.35. Figure 3.34. A 500 kHz Gaussian filter smoothes the four-level 1 megasymbols per second at the input to the FSK modulator. The received signal is mixed with a local carrier to recover the spread digital signal. The rate is called the chip rate, and this is often measured in terms of a number of M chips / sec. 2. In order to spread the sequence using DSSS, an M-chip-long spreading sequence is selected.The M chips of the spreading sequence are replicated N times, with each of the replications being multiplied by one of the N symbols (see Figure 3.2).The symbols of this spread sequence are referred to as “chips.” Vijay K. Garg, in Wireless Communications & Networking, 2007. Both DSSS and FHSS use the 2.4 GHz ISM band (2.4–2.4835 GHz). Direct Sequence Spread Spectrum with Barker code and QPSK International organization of Scientific Research 66 | P a g e Figure 10 depicts transmitter, channel and receiver of DSSS system. CDMA cellphone multiple access technology. Every station in the IEEE 802.11 network uses the same 11-bit sequence. In CDMA applications, the various transmitters which are sharing the channel use different fixed PN sequences which are chosen so that their cross-correlation is low. Also, flexibility in system design and deployment are significantly improved since interference to others is not a problem. Data produced by other dispreading codes would appear as noise and can be discarded as it would be lower in value. . Walter Ciciora, ... Michael Adams, in Modern Cable Television Technology (Second Edition), 2004. In both FDMA and TDMA systems, a time-consuming frequency planning task is required whenever a network changes, whereas no such frequency planning is needed for a CDMA network since each cell uses the same frequencies. The direct-sequence modulation makes the transmitted signal wider in bandwidth than the information bandwidth. In direct sequence spread spectrum (DSSS), the transmitter and receiver contain identical psuedo-random sequence generators producing a pseudo-noise (PN) signal. With DS-CDMA, adjacent microcells share the same frequencies whereas with FDMA/TDMA it is not feasible for adjacent microcells to share the same frequencies because of interference. By the way, according to Wikipedia, the first patent on DSSS was granted in 1942 to a Swiss inventor, Gustav Guanella, and … Main characteristic of spread spectrum systems is their tolerance to interference and low probability of interception [2]. PSD and SCF estimates for captured 802.11b signals. These include: (1) frame exchange between the MAC and PHY under the control of the physical layer convergence procedure (PLCP) sublayer; (2) use of signal carrier and spread spectrum (SS) modulation to transmit data frames over the media under the control of the physical medium dependent (PMD) sublayer; and (3) providing a carrier sense indication back to the MAC to verify activity on the media (see Figure 21.6). This is achievable for local radio systems and transmission lines, but can be much harder to achieve over a wide bandwidth in long distance radio links. Three Non-Overlapping DSSS The code signal is independent of the data and is of a much higher chip rate than the data signal. The spreading of the information is performed by using a spreading signal, called the code signal (see Appendix D). Therefore, we should see non-conjugate CFs of k MHz up to about k = 2 × 11 = 22. DSSS channels for different parts of the world. Since the DSSS channel occupies a 22-MHz band, only the nonoverlapping channels are guaranteed to be free from contention with each other. Figure 25.9. 802.11b channel definitions for North America. Direct sequence spread spectrum (DSSS) is one of the most common spread spectrum (SS) techniques in secure communications. The output signal of … In electronics and telecommunications, it refers to any time varying voltage, current, or electromagnetic wave that carries information. Direct Sequence Spread Spectrum, DSSS Includes: Capacity improvements with DS-CDMA also result from voice activity patterns during two-way conversations, (i.e., times when a party is not talking) that cannot be cost-effectively exploited in FDMA or TDMA systems. If the score is … RF filters     At the intended receiver, despreading is accomplished by cross-correlation of the received spread signal with a synchronized replica of the same code signal used to spread the data. In case of direct sequence spread spectrum (DSSS), each bit in the original signal is denoted by multiple bits in the transmitted signal using a spreading code. This is because the wanted signal becomes larger. For longer intervals, there are many non-conjugate and conjugate CFs for DSSS BPSK. 3.1 Direct Sequence Spread Spectrum Figure (2) depicts transmitter, channel and receiver of DSSS system. Receiver sensitivity must be better than − 80 dBm for a 3% frame error rate. Spread Spectrum and Wi-Fi Basics by Syed M. Mahmud 21. Check out these pages on our website: Figure 2: Comparison of the generation of a narrowband and direct-sequence spread spectrum signals. Frequency synthesizers     The receiver acquires the received code and phase locks its own code to it. The SFD specified is common for all IEEE 802.11 DSSS radios. All three support a 1 to 2 Mbps data rate. For example, two wireless stations operating on channels 1 and 3 would not associate, but carrier sensing may prevent them from transmitting packets simultaneously. The ITU CRC-16 error detection algorithm is used to protect the signal, service, and length field. Minimum required receiver sensitivity is − 75 dBm. 2. DSSS is a low probability of detection (LPD) communications technique, initially developed for military ... the signal and the noise in which the signal is potentially hidden, using test statistics based on either energy or correlation characteristics. Comparison of multiple access methods. An important characteristic of DSSS modulation is that it is rejected by conventional, narrowband receivers that might be sharing the same ISM band. . In practical systems the chip rate is a large integer multiple L of the databit rate. well [1–3]. Over short intervals, then, the SCF for most DSSS BPSK signals is identical to that for a general BPSK signal. DSSS, direct sequence spread spectrum is a form of spread spectrum transmission which uses spreading codes to spread the signal out over a wider bandwidth then would normally be required. The generation of the direct sequence spread spectrum signal (spreading) is shown in Figure 2. Table 6.1 provides a summary of access technologies used for various wireless systems. This, together with the wide bandwidth of the transmitted signal, makes jamming more difficult than for conventional signals. In DSSS, the PN sequence spreads the spectrum of the signal by the chipping rate, resulting in the instantaneous widening of the spectrum. Some often-used sequences with these properties are called Gold and Kasami sequences (Proakis, 1989). With the signal obtained and transmitted, it needs to be decoded within the remote receiver: In this way it can be seen that the original data is recovered exactly by using the same spreading or chip code. The chosen sequences must also have noise-like autocorrelation functions, to help the receiver to synchronise correctly to the partially unknown timing of the transmitter. In the transmitter, the input data stream is XORed with the PN signal before transmission. Because of the chipping code, data can still be recovered without retransmission of the signal, even in the case of damaged data bits. To quantify the increase in bandwidth, a term known as the spreading gain is used. The resulting modulated signal is called DSSS signal. This enabled the process to be visualised more easily. In the DSSS system, the entire bandwidth of the RF carrier is made available to each user. When there is no DSSS signal present at the input to the demodulator there is none-the-less a noise output. The bandwidth of the transmitted signal is therefore L times greater than that of the data stream. This is like a key, only the demodulator that “knows” such a key will be able to demodulate and get the message back. Receiver selectivity     Receiver dynamic range     The spreading … DSSS transmitters use a spreading PN sequence to modulate the baseband signal before transmission. In telecommunications, direct-sequence spread spectrum (DSSS) is a spread-spectrum modulation technique primarily used to reduce overall signal interference. In DSSS, each user has a chipping sequence (or called code, key, etc) that determines how data is encoded and decoded. The use of direct sequence spread spectrum is a powerful principle and has many advantages. Data bits are grouped into symbols of two bits, so each symbol can have one of four levels. ▶︎ Computer Products. After the despreading or removal of the direct-sequence modulation in the receiver, the information bandwidth is restored, while the unintentional and intentional interference is substantially reduced. DS-CDMA radios can, therefore, accommodate more mobile users than FDMA/TDMA radios on the same bandwidth. The technique behind direct sequence spread spectrum, DSSS is at first sight counter-intuitive, but DSSS is used in a number of areas where it enables considerable benefits to be gained. Modulation types & techniques     Chad M. Spooner, Richard B. Nicholls, in Cognitive Radio Technology (Second Edition), 2009. Amplitude modulation     The spreading code spreads the signal across a wider frequency band in … The Direct Sequence Spread Spectrum (DSSS) is a spread-spectrum modulation technique primarily used to reduce overall signal interference in telecommunication. This method provides greater rates of transmission than FHSS, which uses a limited number of frequencies, but fewer channels in a given frequency range. Electronics Notes offers a host of products are very good prices from our shopping pages (in association with Amazon). OSI model for IEEE 802.11 WLAN. The technique requires the DSSS signal to have a constant-modulus spreading code and unrelated message and code-repeat rates. In North America 11 frequencies are used ranging from 2.412 to 2.462 GHz. This is, of course, why its first applications were military. RF circulator     However once received and processed with the correct descrambling codes, it is possible to extract the required data. Direct sequence spread spectrum (DSSS) works somewhat differently. At the physical layer, IEEE 802.11 defines three physical characteristics for WLANs: diffused infrared (baseband), DSSS, and FHSS. ScienceDirect ® is a registered trademark of Elsevier B.V. ScienceDirect ® is a registered trademark of Elsevier B.V. Telecommunications Engineer's Reference Book, Orthogonal Frequency Division Multiplexing, Modern Cable Television Technology (Second Edition), RF and Digital Signal Processing for Software-Defined Radio, Spectrum Sensing Based on Spectral Correlation, Cognitive Radio Technology (Second Edition), Short-range Wireless Communication(Third Edition). communication signals, known as direct sequence spread spectrum (DSSS). Also, the degree of throughput reduction by other 2.4 GHz band users, as well as interference caused to the other users is lower with FHSS. Bluetooth has some of the characteristics of 802.11 FHSS but has advanced well beyond the capabilities of the earlier standard. The Direct Sequence Spread Spectrum modulation makes the transmitted signal wider in bandwidth than the information bandwidth. But instead of a pseudorandom binary sequence (PRBS), an 11-bit Barker code is used as the spreading sequence. In order for FHSS network stations to be synchronized, they must all use the same pseudo-random sequence of frequencies, and their synthesizers must be in step, that is, they must all be tuned to the same frequency channel at the same time. A redundant bit pattern (known as a chipping code) is generated for each bit transmitted. In order to keep the same transmitted bandwidth with a data rate of 2 Mbps, four-level frequency shift-keying is employed. This “key” is in fact a pseudo random sequence (rapid phase transition) also known as pseudo noise (PN). The chipping code in a DSSS is a redundant bit pattern associated with each bit transmitted. The transmit power is directly related to the range that a particular implementation can achieve. In the example shown above, the spreading gain is four, as seen by the fact that four "1"s are generated for each required data bit. 5. This bandwidth holds for both 1 Mbps and 2 Mbps data rates. In anti-jamming (AJ) applications, the transmitter introduces an unpredictable element into the modulation of the signal, known also to the receiver but kept secret from opponents, as in stream ciphering. The first part of the process is to generate the DSSS signal. Signal bandwidth is increased once this key is attached, creating the “spread spectrum” that gives the method its name. However, because DSSS floods the channel it is using, it is also more vulnerable to interference from EM devices operating in the same range. various options of the Wide-Band Direct Sequence Spread Spectrum (WB-DSSS) scheme. The SYNC field is 128 bits (symbols) in length and contains a string of 1s which are scrambled prior to transmission. 4. The received signal is correlated with the generated code, extracting the Information data. The DSSS approach is the basis to implementation of the direct sequence code division multiple access (DS-CDMA) technique introduced by Qualcom. A pseudo-random code is generated, matching the anticipated signal. Channel spacing for IEEE 802.11 DSSS networks. ▶︎ Ham Radio Products. Japan allows the use of all 14 channels. Why is it said that the signal is recovered from below the noise floor ? ▶︎ Ethernet Products. Phase locked loops     Ensure that the NI ELVIS power switch at the back of the unit is off. DSSS is a transmission technology used in LAWN transmissions where a data signal at the sending station is combined with a higher data rate bit sequence, or chipping code, that divides the user data according to a spreading ratio. For everything from distribution to test equipment, components and more, our directory covers it. Maximum allowable transmit power. Direct-sequence spread spectrum (DSSS) is one of two types of spread spectrum radio, the other being frequency-hopping spread spectrum.. DSSS Transmission. CDMA with Direct Sequence Spread Spectrum Jie Gao * February 13, 2007 1 DSSS Overview The idea of CDMA is to use different codes to distinguish different users. In this scenario, one or more data symbols are transmitted each hop. In our first model, we’ll introduce the direct-sequence notion by modifying our familiar rectangular-pulse BPSK signal. Peng Zhang, in Advanced Industrial Control Technology, 2010. This span in North America and most European countries is 2.400 to 2.4835 GHz, and in these regions there are 79 hopping carrier frequencies from 2.402 to 2.480 GHz. Check out our book shop for essential reading and reference on electronics related topics: In Japan only channels at the 2.483 GHz frequency are permitted. An 11-bit Barker code (1, −1, 1, 1, −1, 1, 1, 1, −1, −1, −1) is used for spreading. There are two types of FHSS systems, namely slow frequency hopping and fast frequency hopping. The spectral correlation of DSSS signals is well understood, because over short intervals (relative to the code-repetition interval), the signal is well modeled by PSK or QAM with a symbol rate equal to the DSSS chip rate, and over long intervals, the signal is well modeled as a PSK or QAM signal with a symbol rate equal to the code-repetition rate and a pulse function equal to the repeated chipping sequence. Tony J. Rouphael, in RF and Digital Signal Processing for Software-Defined Radio, 2009. Should there be, in addition, a DSSS signal present, but derived from a PN sequence other than that being used by the demodulator, this will also produce a noise output, since such a signal (it can be shown) looks like random noise. Sender. Copyright © 2021 Elsevier B.V. or its licensors or contributors. ▶︎ Electronics Notes Bookshop. Table 21.5 lists the DSSS channels used in different parts of the world. The spreading sequence or chip sequence has the same data rate as the final output from the spreading multiplier. The specifications for IEEE 802.11 meet the RF emissions guidelines of FCC, ETSI, and the Ministry of Telecommunications. Access technologies for wireless system. A particularly effective and low-cost strategy is to jointly detect several of the cycle frequencies using CF detection. With DSSS, the data is divided and simultaneously transmitted on as many frequencies as possible within a particular frequency band (the channel). Although development of Wi-Fi for significantly increased data rates has based on DSSS, FHSS does have some advantageous features. DSSS is used in a number of areas where its properties have enabled it to provide some unique advantages over other techniques. The maximum allowable radiated power for DSSS PHY varies from region to region (refer to Table 21.6). Alan Bensky, in Short-range Wireless Communication(Third Edition), 2019. In the transmitter, the 11-bit Barker code is applied to a modulo-2 adder together with each of the information bits in the PPDU. Consider an information sequence coded/modulated into a sequence of N modulation symbols. The primary advantage of DS-CDMA is its ability to tolerate a fair amount of interfering signals compared to FDMA and TDMA that typically cannot tolerate any such interference(Figure 6.7). The minimum requirement for processing gain (Gp) in North America and Japan is 10 dB. 11. Many more independent networks can be collocated with virtually no mutual interference using FHSS than with DSSS. Table 21.6.     Return to Radio topics menu . The receiver uses this field to acquire the incoming signal and to synchronize the receiver's carrier tracking and timing prior to receiving the SFD. By using this, the transmission signal of each user can be identified by the separate code when it receives the signal. Transmit and receive DSSS PPDU. Unlike DS systems, FH systems can cover a spectrum of several GHz, which is challenging for DS systems still in today's technology. C. Direct Sequence Spread Spectrum System . Commonly spreading codes may be 64 bits, or even 128 bits long to provide the required performance. As a result of the interference tolerance of CDMA, the problems of frequency band assignment and adjacent cell interference are greatly simplified. Figure 21.8 shows the PPDU frame, which consists of a PLCP preamble, PLCP header, and MAC protocol data unit (MPDU). In general terms, all spread spectrum communications include a key or sequence (also known as the chipping code), which is attached to the communication channel. Uses DSSS Technology U.S. allows the use of channels 1 thru. In the transmitter stage, the baseband data signal m(t) is spread using PN-Sequence c(t).Then, the resultant spread signal s(t) is applied to (BPSK) modulator. When transmitting a DSSS spread spectrum signal, the required data signal is multiplied with what is known as a spreading or chip code data stream. The FHSS physical layer uses GFSK (Gaussian frequency shift keying) modulation, and must restrict transmitted bandwidth to 1 MHz at 20 dB down (from peak carrier). To apply a spread spectrum technique, the relevant spread spectrum code must be applied somewhere in the transmitting chain, before the antenna or receiver. DrM D Macleod MA PhD MIEEE, in Telecommunications Engineer's Reference Book, 1993. However, 26 different hopping sequences (North America and Europe) in any of three defined sets can be used in the same area with low probability of collision. DSSS Using BPSK Multiply BPSK signal, s d (t) = A d(t) cos(2π f c t) by c(t) [takes values +1, -1] to get s(t) = A d(t)c(t) cos(2π f c t) •A = amplitude of signal •f c = carrier frequency •d(t) = discrete function [+1, -1] At receiver, incoming signal multiplied by c(t) oSince, c(t) x c(t) = 1, incoming signal is recovered The non-conjugate CFs for DSSS QPSK are identical to those for DSSS BPSK, and the conjugate CFs are not present. The signal which is spread spectrum, can be demodulated only by a code used for transmission. Fourteen frequency channels are defined for operation across the 2.4 GHz frequency band. While overshadowed by the DSSS PHY, acquaintance with the FHSS option in 802.11 may still be of interest. The output of the modulo-2 adder results in a signal with a data rate that is 10 times higher than the information rate. Often the data is multiplied using the XOR (exclusive OR) function. From: Telecommunications Engineer's Reference Book, 1993, Ido Dubrawsky, in Eleventh Hour Security+, 2010. Had another code been used to regenerate the CDMA spread spectrum signal, then it would have resulted in a random sequence after de-spreading. CDMA basics. On the other hand, FDMA and TDMA radios must be carefully assigned a frequency or time slot to assure that there is no interference with other similar radios. In fast frequency hopping, on the other hand, each data symbol is transmitted over multiple hops and the hopping rate is an integer multiple of the data symbol rate. Receiver sensitivity     Figure 21.9. In DSSS, the narrowband input signal is spread by modulation with a pseudo‐noise (PN) chip sequence. 1. RF attenuators     Can someone please explain the physical / intuitive interpretation of demodulation in DSSS. The service field is reserved for future use. To obtain the sequence is a necessary and essential part to complete the signal system classification and blind despreading. This research developed and validated a generic simulation for a direct sequence spread spectrum (DSSS), using differential phase shift keying (DPSK) and phase shift keying (PSK) modulations, providing the flexibility for assessing intentional interference effect using DSSS quadrature phase shift keying receiver (QPSK) with matched filtering Direct sequence spread spectrum is a form of transmission that looks very similar to white noise over the bandwidth of the transmission. In slow frequency hopping, the symbol rate of the data signal is an integer multiple of the hopping rate. Direct sequence spread spectrum (DSSS) transmission employs a chipping code to “spread” the transmission over a wider frequency band than it would normally occupy. I want to understand what actually happens in the direct sequence spread spectrum demodulator ? ? Therefore, sophisticated filtering and guard band protection is needed with FDMA and TDMA technologies. One such example is Bluetooth where frequency hopping is utilized to spread the spectrum as shown in Figure 3.34 and Figure 3.35. Superhet radio     There is an obvious analogy between this process and stream ciphering (Section 14.8) but with the crucial difference that in DSSS the PN sequence is at a much greater clock frequency than the data stream. However, the implication of such large bandwidths is phase incoherency. Direct-sequence acquisition and tracking A direct-sequence-spread-spectrum receiver must despread the received signal to recover the transmitted data. There are three technical issues are particularly relevant; frequency allocation, frequency roaming, and frequency interference. The bandwidth of the spread spectrum signal will be much wider than the original data stream. The rectangular-pulse BPSK signal is simply a pulse-amplitude modulated signal with In direct sequence spread spectrum (DSSS), the transmitter and receiver contain identical psuedo-random sequence generators producing a pseudo-noise (PN) signal. Each bit in the spreading sequence is called a chip, and this is much shorter than each information bit. The SFD specified is common for all IEEE 802.11 DSSS radios. More Essential Radio Topics: The non-conjugate CFs are harmonics of the code-repetition rate, which is equal to the data rate (bit rate) when the code is repeated for each bit (as it is in 802.11b DSSS BPSK). In the transmitter stage, the baseband data signal m(t) is spread using PN-Sequence c(t) [6]. In the past few years, researchers have done a lot of work to In order to visualise how the direct sequence spread spectrum process operates, the easiest method is to show an example of how the system actually operates in terms of data bits, and how the data is recovered from the DSSS, direct sequence spread spectrum signal. However, the updated versions of 802.11—specifically 802.11a, 802.11b, and 802.11g—have all based their methods of increasing data rates on the broadband channel characteristics of DSSS in 802.11, while being downward compatible with the 1 and 2 Mbps DSSS modes (except for 802.11a which operates on a different frequency band). applications, but have seen more use in commercial applica-tions in later years [1]. This is because, signals with high data rates occupy wider signal bandwidths than those with low data rates. Generally, the longer the chipping code, the more likely it is that the original transmitted data will be properly received. As we will see later, only three independent DSSS networks can be collocated. This can be done by using the SSCA and searching its output for “chains” of CFs separated by 1.0 MHz, or by using a set of FSM-based cycle-frequency searches in narrow bands of cycle frequencies near the nominal values of k MHz. direct sequence spread spectrum (DSSS) or direct sequence code division multiple access (DS-CDMA): Direct sequence spread spectrum, also known as direct sequence code division multiple access (DS-CDMA), is one of two approaches to spread spectrum modulation for digital signal transmission over the airwaves. The ratio of chips to data is known as the spreading ratio: the higher the ratio, the more immune to interference the signal is, because if part of the transmission is corrupted, the data can still be recovered from the remaining part of the chipping code. For DSSS operation, the 2.4-GHz ISM band is divided into three nonoverlapping or six overlapping frequency bands, as shown in Figure 25.9. ▶︎ HDMI Products. U.K. can use channels 1 through 13. This helps to increase the signal's resistance to interference. Receiver strong signal handling     The start of frame delimiter (SFD) contains information that marks the start of the PPDU frame. By continuing you agree to the use of cookies. After a receiver has correlated the received signal with its particular PN pattern, the interference from the other PN sequences is therefore low. Frequency synthesizers are unable to maintain frequency coherency over such wide bandwidths. Nominal deviations of the four levels are ± 72 and ± 216 kHz. The DSSS signal gives LPI (a low probability of intercept) because the total signal power is spread over a wide bandwidth and the signal is noise-like, making it hard to detect. The PMD sublayer takes the binary information bits from the PLCP protocol data unit (PPDU) and converts them into RF signals by using modulation and DSSS techniques (see Figure 21.7). On the other hand, in FHSS, the PN sequence is used to drive the synthesizer and pseudo-randomly hop the signal bandwidth across a much wider band. Further capacity gains for FDMA, TDMA, and CDMA can also result from antenna technology advancement by using directional antennas that allow the microcell area to be divided into sectors. Note: Electronics Notes receives a small commission on sales at no cost to you. Each bit of the PN sequence is called a chip, and the clock rate of the PN generator is called the chip rate.

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