Performance limits of multilevel DPSK

Recently introduced differential phase-shift keying (DPSK) extensions, collectively referred to here as multilevel differential phase (MDP) formats, explore an increase in data throughput for a given bandwidth by effectively multiplexing differential phase encoding and amplitude modulation onto the same fiber link. In this letter, we derive and present analytic models for the quantum limits of bit-error rate for leading MDP modulation formats (binary phase differential phase amplitude-shift keying (DPASK), quaternary phase DPASK), comparing their performance to that of conventional systems.     

The performance of trellis coded multilevel DPSK on a fading mobilesatellite channel

The performance of a trellis-coded multilevel differential phase-shift keying (DPSK) modulation over a mobile satellite channel characterized by additive white Gaussian noise (AWGN) and slow Rician fading is presented. Both the optimum and Gaussian (suboptimum) decoding metrics are considered, with performance results given only for the latter. Analytical results (upper bounds on bit error rate) are obtained wherever possible and illustrated by several numerical examples. Also given are simulation results which are more indicative of the exact system performance. Comparisons with results previously obtained for coherent detection of the same coded modulations are presented     

Spectrum efficiency of multilevel modulation schemes in mobileradio communications

Lee (1989) has produced equations describing spectrum efficiency for modulation schemes operating in cellular environments. The present authors consider the performance of a range of multilevel modulation schemes when these spectrum efficiency equations are applied. They then proceed to adapt these efficiency equations for use in microcells before considering the performance of multilevel modulation within this environment. The results show that the preferred modulation scheme depends on the BER required, with 4 level PSK being preferred in conventional cells, and variable 16 level QAM, or 32 or 64 level QAM being suitable in microcells, particularly when a high SNR is available     

Performance limits of coded diversity methods for transmitterantenna arrays

Several aspects of the design and optimization of coded multiple-antenna transmission diversity methods for slowly time-varying channels are explored from an information-theoretic perspective. Both optimized vector-coded systems, which can achieve the maximum possible performance, and suboptimal scalar-coded systems, which reduce complexity by exploiting suitably designed linear precoding, are investigated. The achievable rates and associated outage characteristics of these spatial diversity schemes are evaluated and compared, both for the case when temporal diversity is being jointly exploited and for the case when it is not. Complexity and implementation issues more generally are also discussed     

Soft-limiter receivers for coded DS/DPSK systems

The performance of a soft-limiter metric and a quantized soft-limiter metric is evaluated for coded DS/DPSK (direct sequence/differential phase shift keying) in the presence of worst case pulse jamming and background noise. The metrics are easy to implement and do not require jammer state information. Instead they rely on the use of receiver thresholds, which must be adjusted according to the code rate and the received bit-energy-to-background-noise ratio. The performance of the metrics is evaluated by using the cutoff rate criterion and a number of specific convolutional and block codes. It is shown that the metrics can offer a significant soft-decision decoding gain and can perform to within 0.5-1.5 dB of the maximum-likelihood soft-decision metric with perfect jammer state information     

Concatenated multilevel block coded modulation

Encoding and decoding schemes for concatenated multilevel block codes are presented. By one of these structures, a real coding gain of 5.6-7.4 dB for the bit error range of 10^-6 to 10^-9 is achieved for transmission through the additive white Gaussian noise channel. Also, a rather large asymptotic coding gain is obtained. The new coding schemes have very low decoding complexity and increased coding gain in comparison with the conventional block and trellis coded modulation structures. A few design rules for concatenated (single and) multilevel block codes with large coding gain are also provided     

Performance limits of Reed-Solomon coded CDMA with orthogonalsignaling in a Rayleigh-fading channel

The asymptotic performance of Reed-Solomon (RS)-coded M-ary orthogonal signaling with ratio-threshold test (RTT) type demodulation in a Rayleigh-fading channel is considered. We show that the minimum E¯_b/N₀ needed for error-free communication is eln2 (2.75 dB) with RTT, and 4.79 (6.8 dB) with hard decisions. The optimum code rate that minimizes the required E¯_b/N₀ is e^-1 with RTT and 0.46 with hard decision, and the optimum ratio threshold approaches 1 for large M. Next, we investigate the fundamental limit in a direct-sequence spread-spectrum multiple-access (DS/SSMA) system employing an M-ary orthogonal code of length N=Mm, which is obtained by spreading every row of an M×M Hadamard matrix with a user-specific random sequence of length N. We derive the minimum E¯_b/N₀ for error-free communication as a function of the number of users, the optimum code rate that minimizes E¯_B/N₀, and the maximum limit on the total information transmission rate. Then, we consider a multirate DS/SSMA system, where a population of users simultaneously transmit at different power levels a variety of traffic types of different information rates. We derive the minimum required E¯_B/n₀ and the optimum code rate for each traffic type     

Analysis of a multiple-cell direct-sequence CDMA cellular mobileradio system

The performance of a multiple-cell direct-sequence code division multiple-access cellular radio system is evaluated. Approximate expressions are obtained for the area-averaged bit error probability and the area-averaged outage probability for both the uplink and downlink channels. The analysis accounts for the effects of path loss, multipath fading, multiple-access interference, and background noise. Two types of differentially coherent receivers are considered: a multipath rejection receiver and a RAKE receiver with predetection selective combining. Macroscopic base station diversity techniques and uplink and downlink power control are also topics of discussion     

Performance limits for channelized cellular telephone systems

Studies the performance of channel assignment algorithms for “channelized” (e.g., FDMA or TDMA) cellular telephone systems, via mathematical models, each of which is characterized by a pair (H,p), where H is a hypergraph describing the channel reuse restrictions, and p is a probability vector describing the variation of traffic intensity from cell to cell. For a given channel assignment algorithm, the authors define T(r) to be the amount of carried traffic, as a function of the offered traffic, where both r and T(r) are measured in Erlangs per channel. They show that for a given H and p, there exists a function T_H,p(r), which can be computed by linear programming, such that for every channel assignment algorithm, T(r)⩽T_H,p(r). Moreover, they show that there exist channel assignment algorithms whose performance approaches T_H,p (r) arbitrarily closely as the number of channels increases. As a corollary, they show that for a given (H,p) there is a number r₀ , which also can be computed by linear programming, such that if the offered traffic exceeds r₀, then for any channel assignment algorithm, a positive fraction of all call requests must be blocked, whereas if the offered traffic is less than r₀, all call requests can be honored, if the number of channels is sufficiently large. The authors call r₀, whose units are Erlangs per channel, the capacity of the cellular system     

Simplified block adaptive diversity equalizer for cellular mobileradio

We propose a reduced complexity antenna diversity combiner-equalizer receiver structure to combat multipath fading in cellular mobile radio (CMR) communications. The technique utilizes block adaptation based on interpolated channel estimates and linear or decision feedback equalization. The receiver offers complexity reduction relative to previously proposed block adaptation methods without sacrificing performance     

Uncoded and coded performance of MFSK and DPSK in Nakagami fadingchannels

The author presents uncoded and coded performance results for noncoherent M-ary frequency-shift keying (MFSK) and differentially coherent binary phase-shift keying (DPSK) in a slow nonselective Nakagami-m (1960) fading channel. He gives simple expressions for the asymptotic slopes of probability of bit error for large signal-to-noise ratio and shows that the effective order of diversity compared to an uncoded Rayleigh channel is the product of two parameters, one for the channel and one for the code. He also compares the uncoded Nakagami-m results to those of the Rician channel in order to show performance differences between these two generalized fading channel models     

Iterative decoding of coded and interleaved noncoherent multiplesymbol detected DPSK

A new receiver for coded and interleaved DPSK based on multiple symbol differential detection (MSDD) and iterative (`turbo') decoding is proposed. Performance close to that of coherent detection over an AWGN channel is demonstrated by simulations     

Channel quality estimation and rate adaptation for cellular mobileradio

We propose a technique to measure channel quality in terms of signal-to-interference plus noise ratio (SINR) for the transmission of signals over fading channels. The Euclidean distance (ED) metric, associated with the decoded information sequence or a suitable modification thereof, is used as a channel quality measure. Simulations show that the filtered or averaged metric is a reliable channel quality measure which remains consistent across different coded modulation schemes and at different mobile speeds. The average scaled ED metric can be mapped to the SINR per symbol. We propose the use of this SINR estimate for data rate adaptation, in addition to mobile assisted handoff (MAHO) and power control. We particularly focus on data rate adaptation and propose a set of coded modulation schemes which utilize the SINR estimate to adapt between modulations, thus improving the data throughput. Simulation results show that the proposed metric works well across the entire range of Dopplers to provide near-optimal rate adaptation to average SINR. This method of adaptation averages out short-term variations due to Rayleigh fading and adapts to the long-term effects such as shadowing. At low Dopplers, the metric can track Rayleigh fading and match the rate to a short-term average of the SINR, thus further increasing throughput     

Performance of rate compatible punctured Turbo-codes for mobileradio applications

Future mobile radio systems like the European UMTS (universal mobile telecommunications system) will provide packet oriented data services with data rates up to 2 Mbit/s. Therefore, flexible and adaptive error correction coding must be deployed. Recently, rate compatible punctured Turbo-codes (RCPTCs) have been proposed. The authors discuss a design method for such codes and illustrate its viability by showing the performance results for an RCPTC with a block size of 672 bits     

A wide-band propagation model based on UTD for cellular mobileradio communications

The present wide-band propagation model based on uniform geometrical theory of diffraction (UTD) for cellular mobile radio communications includes two major contributions. First, a UTD-based narrow-band channel transfer function containing both the diffracted electric field and the reflection of diffracted electric fields is derived. Not only is it an important element of the wide-band modeling method, but it also leads to a total path-loss prediction model verified by comparisons with previously published theoretical and experimental results. In particular, the distance for horizontal placement on the street allows one to calculate the ray-path length difference (used in wide-band modeling) for the diffracted field and the reflection. Second, new refinements (including a number of explicit-form expressions to an existing method experimentally confirmed, simulating wide-band radiowave propagation for rural environments including terrain profiles) are added, making it applicable here. The method generates the time-domain path loss, wide-band path loss, and the relative power in the frequency domain. The time-domain path loss physically interprets and reasonably predicts the power delay profiles. The presence of this and similar power delay profiles, as well as the behavior of the relative power in the frequency domain, has been confirmed by existing wide-band propagation measurements. The value of the wide-band path loss is of the order of the total path loss at the carrier frequency     

CPM 编码调制系统的基本性能限

针对CPM系统的信道容量研究结果进行了综述,并推导计算了Rayleigh衰落信道下CPM的容量分析方法与计算结果。首先回顾了CPM系统的基本概念及其有限状态马尔可夫模型,并对AWGN信道下CPM的可达信息速率计算方法进行了讨论;然后将其推广到Rayleigh衰落信道,推导出在该信道下计算CPM容量的算法。考虑了接收端已知信道状态信息及未知信道状态信息2种情况。在导出容量计算的算法后,通过Monte Carlo仿真给出了在AWGN及Rayleigh衰落信道下几种典型CPM方案的容量曲线。     

Performance of DPSK mobile receiver in impulse noise

The authors present a performance analysis of L-diversity DPSK receivers over frequency non-selective Rayleigh fading channels in Middleton's class A impulse noise. The analysis is exact and is shown by simulation to be accurate     

Phase-noise-induced performance limits for DPSK modulation with andwithout frequency feedback

The effect of phase noise on the performance of differential phase shift keying (DPSK) is analyzed for four different receiver structures. The phase noise model used is more general than the standard Brownian motion model. It allows the observation of the effect of frequency feedback stabilization on system performance. The asymptotic performance in the limit as the signal-to-noise ratio tends to infinity is considered. The results show that feedback stabilization results in a considerable performance improvement. For example, in a narrowband receiver this scheme results in an effective linewidth reduction by a factor of 12.5 when the feedback bandwidth is 0.8 times the bit rate, and by a factor of 42 when the feedback bandwidth is 1.6 times the bit rate. Therefore, frequency feedback reduces the minimum required data rate for a given laser linewidth, or increases the maximum linewidth allowed for a given data rate. The performance of the narrowband receiver in the presence of both additive and phase noises is determined and a dramatic improvement with feedback is shown     

Simple and accurate methods for outage analysis in cellular mobileradio systems-a unified approach

Two unified expressions for computing the refined outage criterion (which considers the receiver noise) in cellular mobile radio systems are derived using the Laplace and Fourier inversion formulas. Since these expressions do not impose any restrictions on the signal statistics while being easy to program, they provide a powerful tool for outage analysis over generalized fading channels. We also assess compatibility and applicability of previously published approaches that treat noise as cochannel interference (noise-limited model) or consider a minimum detectable receiver signal threshold and receiver noise. The outage probability in an interference-limited case can be evaluated directly by setting the minimum power threshold to zero. The analysis of correlated interferers is presented. Results are also developed for a random number of interferers. Several new closed-form expressions for the outage probability are also derived. Some previous studies have suggested approximating Rician desired signal statistics by a Nakagami-m (1960) model (with positive integer fading severity index) to circumvent the difficulty in evaluating the outage in Rician fading. The suitability of this approximation is examined by comparing the outage performance under these two fading conditions. Surprisingly, some basic results for Nakagami-m channel have been overlooked, which has led to misleadingly optimistic results with the Nakagami-m approximation model. However, similar approximation for the interferer signals is valid