Performance of a Binary PPM Ultra-Wideband Communication System with Direct Sequence Spreading for Multiple Access

In this paper, we present an analysis of the BER performance of an ultra-wideband (UWB) system with pulse position modulation (PPM) for data modulation and direct sequence (DS) spreading for multiple access over indoor lognormal fading channels. A rake receiver is used to combine a subset of the resolvable multipath components using the maximal ratio combining technique. Inter-path and multiple-access interferences are modeled and incorporated into the bit-error-rate expressions. The analytical and simulation results allow one to quantify many critical aspects of a DS-PPM UWB system such as the gain of the optimally spaced signaling scheme over the orthogonal signaling scheme, the potential error floor given a specific channel multipath delay spread and the number of interfering users, tolerance of the system to timing jitter, and impact of user codes.     

Pulse Position Amplitude Modulation for Time-Hopping Multiple-Access UWB Communications

In this letter, we propose a new modulation scheme called pulse position amplitude modulation (PPAM) for ultra-wideband (UWB) communication systems. PPAM combines pulse position modulation and pulse amplitude modulation to provide good system performance and low computational complexity. The channel capacity of PPAM is determined for a time-hopping multiple-access UWB communication system. The error probability and performance bounds are derived for a multiuser environment.     

跳时脉幅脉位混合调制超宽带通信性能研究

针对目前超宽带通信调制方式误码率高的问题，提出正交脉冲脉幅脉位混合调制（OAPPM）改善系统性能的方法。OAPPM调制方式是把信息调制在信号的位置和幅度上，接收端利用最佳检测器进行接收。文中分析了TH—OAPPMUWB系统的信道容量和误符号率并进行了仿真。结果表明：该方法与传统的PPM和PAM相比，降低了误符号率和系统复杂度，较好地改善了UWB通信系统性能。     

超宽带波形和调制技术研究

研究了几种不同的脉冲成形和调制技术,并对其性能进行了分析。仿真结果表明,在AWGN信道和瑞利衰落信道下,不同的脉冲形状对脉冲位置调制（PPM）的性能影响较大,而对二进制相移键控调制（BPSK）和开关键控调制（OOK）影响较小,且当采用RZ-Manchester脉冲时,BPSK调制技术下的误比特率（BER）性能在两种信道下均达到最好。     

TH-BPPM UWB系统在Nakagami-m衰落信道下的性能研究

跳时双正交脉冲位置调制（TH-BPPM）在超宽带（UWB）衰落信道的通信系统性能研究是基于超宽带室内无线信道进行研究的。频率选择性衰落是多径环境需要重点考虑的因素之一,在单用户情况下经常采用高斯近似法。利用等效瞬时信噪比和在AWGN信道下的误码率公式推导得出错误概率公式,并由Matlab仿真得到结论。     

Performance analysis of dual pulse transmission in UWB channels

A dual pulse transmission scheme with autocorrelation detector has recently been proposed for robust and low complexity UWB communications. This letter present bit error rate expressions of the binary pulse amplitude modulated dual pulse scheme in realistic UWB channels. The semi-analytical solutions are verified by simulation results for IEEE 802.15.3a channels.     

On the Amplify-and-Forward Cooperative Diversity with Time-Hopping Ultra-Wideband Communications

In this paper, we extend the Amplify-and-Forward cooperative diversity scheme to the context of impulse radio ultra wideband (IR-UWB). In particular, we present the construction of three families of minimal-delay and totally-real distributed algebraic space-time (ST) codes suitable for IR-UWB. The first family encodes adjacent symbols and is based on totally-real cyclic division algebras. The second family encodes the pulses used to transmit one information symbol and permits to achieve high performance levels with lower complexity. Both families of codes achieve full rate, full diversity with non-vanishing determinants for various number of relays. These schemes can be associated with pulse position modulation (PPM), pulse amplitude modulation (PAM) and hybrid pulse position and amplitude modulation (PPM-PAM). The third family of codes is information-lossless and does not require any pulse repetitions. It is specific to M-PPM-M'-PAM with M ges 3 and for all values of M'. Simulations performed over realistic indoor UWB channels are provided to verify the theoretical results.     

Novel UWB Transceiver for WBAN Networks: A Study on AWGN Channels

A novel ultra‐wideband (UWB) transceiver structure is presented to be used in wireless body area networks (WBANs). In the proposed structure, a data channel and a control channel are combined into a single transmission signal. In the signal, a modulation method mixing pulse position modulation and pulse amplitude modulation is proposed. A mathematical framework calculating the power spectrum density of the proposed pulse‐based signal evaluates its coexistence with conventional radio systems. The transceiver structure is discussed, and the receiving performance is investigated in the additive white Gaussian noise channel. It is demonstrated that the proposed scheme is easier to match to the UWB emission mask than conventional UWB systems. The proposed scheme achieves the data rate requirement of WBAN; the logical control channel achieves better receiving performance than the logical data channel, which is useful for controlling and maintaining networks. The proposed scheme is also easy to implement.     

Performances of EGC and MRC diversity for UWB PAPM systems in IEEE channel models

Accurate approximations to the bit error rates of equal gain combining and maximal ratio combining diversity are obtained for pulse-amplitude-and-position-modulation operating in IEEE ultra-wide bandwidth (UWB) channel models. Numerical results are presented to show the accuracy of the approximations for the IEEE CM1 and CM3 UWB channel models. Results for pulse amplitude modulation and pulse position modulation are obtained as special cases of the more general results. Precise estimates of the loss of equal gain combining relative to maximal ratio combining are obtained for both lineof- sight CM1 and non-line-of-sight CM3 channels. Noteworthy, while the performance loss of equal gain combining with respect to maximal ratio combining is less than 0.4 dB for the non-lineof- sight channel, it can be as much as 2 dB for the line-of-sight channel.     

On the capacity of log-normal fading channels

In this letter we provide an analytical expression for the moments of the capacity for the log-normal fading channel. Since the developed expression involves infinite series, we show that the error that results from the truncation of these series is insignificant. We also analyze in more details the ergodic capacity by giving a simpler expression for the remainder of the truncated series. Relying on the fact that the sum of log-normal Random Variables (RV) is well approximated by another lognormal RV, we further utilize the obtained results to approximate the capacity of diversity combining techniques in correlated lognormal fading channels. The results that we provide in this letter are an important tool for measuring the performance of communication links in a log-normal environment.     

UWB multi-pulse position modulation for high data-rate wireless application

1 Introduction UWB technology is considered to be a good candidate for future short-range high-data rate wireless communications [1, 2], and modulation plays an important role in UWB wireless communication systems. There are several modulation schemes possible for UWB, such as pulse position modulation (PPM), pulse amplitude modulation (PAM), On-Off keying (OOK), binary phase-shift keying (BPSK), and so on. Reference [3] provides the analysis result of the different modulation methods…     

相关衰落信道上MIMO系统中组合SC/MRC的性能分析

研究相关瑞利衰落信道上MIMO系统中组合发射机选择合并(SC)/接收机最大比合并(MRC)的天线分集系统性能.使用矩生成函数方法,推导相关瑞利衰落信道上采用组合SC/MRC天线分集争相干检测的M进制相移键控(MPSK),M进制正交幅度调制(MQAM),M进制脉冲幅度调制(MPAM)等几种M进制数字调制方式的误符号率精确表达式.数值计算结果阐明相关性和天线阵结构对采用组合SC/MRC天线分集的几种M进制数字调制方式的平均误符号率性能的影响.     

Multiuser detection of time-hopping PPM UWB system in the presence of multipath fading

Ultra-wideband (UWB) impulse radio (IR) systems are currently being considered for several applications due to their attractive features that include low-power carrierless and ample multipath diversity. Among the various modulation and multiple-access schemes, time-hopping (TH) pulse position modulation (PPM) is a popular technique in application. Most past works rely on strict power control and perform single-user detection (matched filtering) on the desired signal. This paper aims to apply multiuser detection techniques in binary PPM (BPPM) UWB IR multiple-access systems. Moreover, we consider frequency-selective multipath fading channels to account for the wireless cellular environment. A class of linear multiuser detectors (LMDs) is applied to extract the information bits while eliminating multiuser interference (MUI) in the presence of multipath fading. Simulation results are provided to compare the performance of different LMDs.     

Space–Time Coding for Multiuser Ultra-Wideband Communications

In this paper, we present the construction of full rate, fully diverse, and totally real space-time (ST) codes for ultra-wideband (UWB) transmissions. In particular, we construct two families of codes adapted to real carrierless UWB communications that employ pulse position modulation, pulse amplitude modulation, or a combination of the two. The first family encodes adjacent symbols and is constructed from totally real cyclic division algebras. The second family encodes the pulses used to convey one information symbol, and permits achieving high performance levels with reduced complexity. The first family of codes achieves only a fraction of the coding gain of the second one. Moreover, these coding gains are independent from the size of the transmitted constellation. For time-hopping multiple-access channels, the amplitude spreading code associated with the second family of codes is taken to be user-specific. In this case, a simple design criterion is proposed, and spreading matrices constructed according to this criterion permit reducing the level of multiple-access interference (MAI). Simulations performed over realistic indoor UWB channels verify the theoretical claims and show high performance levels and better immunity against MAI     

Space–Time Coding for Multiuser Ultra-Wideband Communications

In this paper, we present the construction of full-rate, fully diverse, and totally real space–time (ST) codes for ultra-wideband (UWB) transmissions. In particular, we construct two families of codes adapted to real carrierless UWB communications that employ pulse position modulation, pulse amplitude modulation, or a combination of the two. The first family encodes adjacent symbols and is constructed from totally real cyclic division algebras. The second family encodes the pulses used to convey one information symbol, and permits achieving high performance levels with reduced complexity. The first family of codes achieves only a fraction of the coding gain of the second one. Moreover, these coding gains are independent from the size of the transmitted constellation. For time-hopping multiple-access channels, the amplitude spreading code associated with the second family of codes is taken to be user-specific. In this case, a simple design criterion is proposed, and spreading matrices constructed according to this criterion permit reducing the level of multiple-access interference (MAI). Performance over realistic indoor UWB channels verify the theoretical claims, and show high performance levels and better immunity against MAI.     

IR-UWB系统几种新型调制技术

IR-UWB(Impulse Radio-Ultra wide Bandwidth,冲激无线电-超宽带技术)是短距离无线通信中一个非常有前景的技术.该文介绍了几种有关IR-UWB信号的比较新型的调制技术,例如伪混沌编码跳时调制、脉冲位置幅度调制、自适应调制等,分析了其调制方法的基本原理,并给出了误码率分析.     

A packet reservation multiple access assisted cordlesstelecommunication scheme

A packet reservation multiple access (PRMA) assisted microcellular cordless telecommunications (CT) system is investigated for office type environments in absence of cochannel interference. The objective speech quality is found as a function of channel signal-to-noise ratio (SNR) for transmissions over narrowband Rayleigh fading channels, parameterized with the number of PRA users. A moderate complexity 16-ary CT scheme constituted by a 4-bit/symbol 32-kbps adaptive differential pulse code modulation (ADPCM) speech codec, Reed-Solomon forward error correction (FEC) codec, and diversity-assisted 16-level star quadrature amplitude modulation (16-StQAM) modem is proposed. The 264-kBd 20-slot PRMA scheme supports 36 users while maintaining virtually imperceptible speech degradation for channel SNRs in excess of about 25 dB, and for a mobile speed of 2 mi/h if the signal-to-interference ratio (SIR) is above 30 dB     

Performance of DPSK with Convolutional Encoding on Time-Varying Fading Channels

The bit error probability performance of a differentiallycoherent phase-shift keyed (DPSK) modem with convolutional encoding and Viterbi decoding on time-varying fading channels is examined. We consider both the Rician and the lognormal channels. Bit error probability upper bounds on fully-interleaved (zero-memory) fading channels are derived and substantiated by computer simulation. It is shown that the resulting coded system performance is a relatively insensitive function of the choice of channel model provided that the channel parameters are related according to the correspondence developed as part of this paper. Finally, a comparison of DPSK with a number of other modulation strategies is provided.     

基于PM 的多功能超宽带调制技术的研究

基于相位调制器(PM)级联高斯带通滤波器,提出了一种超宽带(UWB)多功能调制方案,可以实现通断键控(OOK)、脉冲极性调制(PBM)和脉冲形状调制(PSM)。该方案结构简单,只需单个光源,利用率较高,仅改变比特序列发生器(BSG)的编码就可实现三种UWB调制格式间的灵活切换;产生的三种信号只包含一个波长,在光纤中传输时无需复杂的非线性控制和色散管理。使用光通信软件Optisystem进行模拟,研究了光源功率、调制速率以及两支路PM和滤波器系统误差的影响,对OOK、PBM和PSM信号的传输性能进行了分析。结果表明,光源功率和调制速率在一定范围内变化时,可以获得性能最佳的UWB调制信号。     

Nakagami衰落信道上组合SC/MRC的性能分析

研究Nakagami衰落信道上组合发射机选择合并(SC)/接收机最大比合并(MRC)天线分集系统的性能.使用矩生成函数方法,推导采用组合SC/MRC天线分集和相干检测的MPSK(M进制相移键控)、MQAM(M进制正交幅度调制)、MPAM(M进制脉冲幅度调制)、BFSK(二进制频移键控)、最小相关BFSK(BFSKmin)、差分编码BPSK(DE-BPSK)和预编码MSK(最小频移键控)等几种M进制数字调制方式在Nakagami衰落信道上的误符号率性能,获得了M进制数字调制系统误符号率性能的精确数学表达式.数值计算结果阐明了发射天线和接收天线数目以及衰落参数对数字调制系统误符号率性能的影响.