Performance Evaluation of Hybrid Cooperation Protocol in IEEE 802.16e

Wide-band digital indoor and future mobile communication systems are being developed in the quasi-millimeter and millimeter wave frequency bands. In such high-speed systems, the degradation of transmission quality by multipath fading constitutes a limiting barrier. Multipath fading, which results from reflection, refraction and scattering of radio waves by buildings and other structures, gives rise to more than one path reaching the receiver and produces a distorted version of the transmitted signal. In mobile and indoor communication systems it cannot be eliminated, therefore the multipath channel must be well characterized in order to reduce its effect in the design of such systems. The objective of this research is to study the multipath fading and delay spread effects due to buildings in an urban propagation channel. In particular, the effects of the building materials, shapes and number of buildings on multipath fading are being studied.

In wide-band mobile communication systems, the received signal-level variation characteristics are different from those in narrow-band systems. To express the variation from narrow-band to wide-band transmissions, a new propagation parameter was proposed called equivalent received bandwidth, which is the product of receiver bandwidth 2/spl Delta/f and maximum difference in path lengths /spl Delta/L/sub max/. On the other hand, Nakagami-m (1960) distribution offers a more flexible distribution of received signal-level variations in narrowband mobile channels. Therefore, we have expressed the level variation in narrow and wide band using the Nakagami-m distribution as function of 2/spl Delta/f/spl Delta/L/sub max/, and evaluated the distribution by computer simulation.

The use of high level trellis-coded modulation with fading counter measure techniques such as equalisation, space diversity, slow frequency hopping and interleaving is proposed for wideband mobile communications. The symbol error rate (SER) performance of those systems on presence of additive white Gaussian noise (AWGN), co-channel interference (CCI), Intersymbol interference (ISI) and frequency selective multipath Rayleigh fading are investigated. Several combining schemes for equalisers and diversity are evaluated by computer simulation. It shows that by choosing a proper interleaving size, number of the frequency hopping and the combining scheme of equaliser and space diversity, the proposed system gives considerable performance improvement and can cope with the frequency selective multipath fading in wideband mobile communication systems.

The use of high level trellis-coded modulation such as TCM 16-QAM, with equalization, diversity, interleaving and slow frequency hopping is investigated for wideband mobile communications. The symbol error rate (SER) performance of those systems in presence of intersymbol interference (ISI) and Rayleigh fading is evaluated by theoretical analysis and computer simulation. Several schemes of combining equalizers with diversity are evaluated by computer simulations. It shows that by choosing a proper interleaving size, number of the frequency hopping and the combining scheme of equalization and space diversity, the proposed system gives considerable performance improvement and can cope with the frequency selective multipath fading in wideband mobile communication systems.

The MIMO transmission against a smart attacker has recently been formulated as a noncollaborative game, in which both the MIMO transmitter and the malicious attacker try to maximize their predefined utilities. In this paper, by carefully analyzing the Nash Equilibrium (NE), we focus on the conditions, in which the gaming results incline to the malicious attacker instead of the MIMO transmitter. In this adverse case, it is highly desirable to develop an effective mechanism to suppress the attack intention by the attacker for better secure communication. Motivated by this, an adaptive secure MIMO transmission scheme was proposed to make the MIMO transmitter better resist malicious attackers in adverse channel conditions. Compared with the existing gaming-based strategy, not only the transmit power of the MIMO transmitter but also the transmission probability will be adjusted in the proposed adaptive secure transmission scheme. Our analysis results show that the proposed scheme can be regarded as a generalized adaptive transmission one, i.e., when the adaptive transmit power policy is enough to suppress the attack motivation, the proposed scheme will be reduced to the adaptive power control scheme; otherwise, both the adaptive transmit power and the adaptive probabilistic transmission can be employed to suppress the attack motivation. The analysis results confirm us that the proposed adaptive transmission scheme provides us a choice to enhance the secure MIMO transmission performance in adverse conditions.

This paper deals with throughput oriented adaptive modulation and coding (AMC) techniques combined with cooperative protocols where terminals are constrained by half-duplex assumption and average total network power. We propose a novel hybrid cooperation protocol that switches from cooperative to non-cooperative transmission based on the momentary direct source-destination link quality. Then, we propose an <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">hybrid</i> cooperative <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">AMC</i> mechanism, which combines AMC with hybrid cooperation. Simulation results show that our proposal improves the average system performance and reduces the average cooperation signaling cost.

A Multi Frequency wide Band Rectangular Patch Micro strip Antenna with T Shaped Slot with shorting wall (RPMATSSSW) is designed on glass epoxy FR-4 substrate. The performance of this antenna is compared with that of a simple rectangular patch antenna. The simulated results for this antenna are optimized by varying position, length and width of T shaped slot and also by introducing two shorting wall. The results indicate that the designed structure resonate at various closely spaced frequencies (as shown in figure-4) which are use full for Ultra wide band (UWB) communication systems, which has been allocated IEEE 802.15.3a standard for specifies the frequency range 3.1GHz to 10.6GHz. The Modified antenna offers much improved bandwidth 76.71% at central resonance frequency 7.62GHz in comparison to a rectangular patch antenna (having band width 3.27%). The directivity of antenna also improves significantly at some of the resonance frequencies.

In this paper, three new ultra wideband (UWB) communication systems with quadrature-phase shift keying (QPSK) impulse modulation are proposed. First, direct-sequence (DS) multiple-access scheme is applied. The second proposed system is based on time-hopping (TH) multiple-access scheme. The last proposed system applies TH multiple-access scheme with QPSK impulse modulation and pulse position modulation (PPM). The conventional UWB communications as TH scheme with PPM modulation and DS scheme with binary-phase shift keying (BPSK) are used to compare. The simulation results show that all proposed UWB communication systems can provide obviously better performances compared with the conventional TH-PPM and DS-BPSK UWB communication systems. The comparisons in aspects of transmission bit rate and the number of users are also investigated.

Optical space communication will use clouds as part of communication channels. Propagation of optical pulses through clouds causes widening and deformation in the time domain and attenuation of the pulse radiant power. These effects decrease the received signal and limit the information bandwidth of the communication system. This work defines typical characteristics of optical pulse propagation through clouds. Characteristics of the optical pulses are calculated using Monte-Carlo simulation. Based on these characteristics a model for optimum performance of digital optical communication through clouds is presented. Examples for practical communication systems are given. An adaptive method to improve and in some cases to make possible communication is suggested. Comparison and analysis of two models of communication systems in cloud channels are presented: (1) adaptive transmitter and standard receiver (semi-adaptive system) and (2) adaptive transmitter and receiver (adaptive system). An improvement of more than eight orders of magnitude in bit error rate under certain conditions is possible with the new adaptive system model.

The emerging Ultra Wideband (UWB) communication system is highly suitable for wireless multimedia connectivity in home and SOHO (Small Office Home Office) scenarios. As such, UWB is an example of enabling technology for Fourth Generation (4G) communication systems designed to replace Bluetooth communications. Indeed, UWB radio will revolutionise Wireless Personal Area Networks (WPANs) allowing the wireless transmissions of high data rates (hundreds of Mbps) over short distances (0-10 m). This paper deals with the design and performance of M-ary PSK based Multiband Orthogonal Frequency Division Multiplexing (MB-OFDM) UWB communication system over realistic multipath-fading modified Saleh-Valenzuela (S-V) channel environments as specified by the IEEE 802.15.3a Task Group. A system level analysis is addressed to improve the throughput and transmission range as a function of coded BER, link PER, received SNR and distance through extensive Monte Carlo simulations. (6 pages)

A major challenge in the design of next generation wireless communication systems is to achieve both reliable and spectral efficient communication with large coverage range. To tackle this problem, advanced diversity techniques combinedwith adaptive mechanisms have to be designed in order to combat or even exploit the variability of the radio propagation medium across time, frequency and space. Diversity techniques create signal redundancy, by repeating the information across multiple, independent channel realizations. This is accomplished by allowing the receiver to experience the average channel effect rather than an instantaneous fade. As a consequence diversity techniques improve the link reliability at the expense of the system spectral efficiency. By adjusting the transmission parameters to the momentary link quality, adaptive mechanisms aim at improving both spectral efficiency and link reliability. Nevertheless, in order to guarantee the Quality of Service (QoS) constraints from the upper layers, adaptive mechanisms implement a sub-optimal trade-off between link robustness and bandwidth efficiency (Calvanese Strinati E., 2006). Therefore in this chapter we propose and analyze a novel cooperation protocol, the hybrid cooperation protocol and we combine it with link adaptation techniques such as Adaptive Modulation and Coding (AMC) and power allocation. Our task is to minimize the outage probability and maximize the spectral efficiency of transmission, while limiting the cooperation cost in terms of MAC signalling overhead. The scientific content of this chapter is based on some innovative results presented in three conference papers (E. Calvanese Strinati and S. Yang and J-C. Belfiore, 2007) (E. Calvanese Strinati and Luc Maret, 2008) (M. Baydar and E. Calvanese Strinati and J. C. Belfiore, 2008) presented in 2007 and 2008. The goals of this chapter are for the reader to have an understanding of cooperative communication issues and challenges and, to be well informed of the state-of-the-art research development. Eventually, the chapter will present what we have done to improve the performance of currently proposed cooperation techniques, comparing performance of our proposed approaches with state-of-the-art one. A critical discussion on advantages and weakness of the proposed approaches, including future research axes, will conclude the chapter. The innovative contribution in this chapter is threefold. First, in this chapter we introduce and details challenges and possible solutions for the so-called cooperative diversity (E. Erkip A. Sendonaris and B. Aazhang: Part I, 2003; E. Erkip A. Sendonaris and B. Aazhang: Part II, 2003) techniques where a source terminal cooperates with several relays to exploited the spatial diversity in a distributed manner. From a physical 9

New ultra wideband (UWB) communication system using quadrature-phase shift keying (QPSK) impulse modulation with time-hopping (TH) multiple-access scheme is proposed. The simulation results in multipath channel show that the proposed UWB communication system can provide better performances compared with conventional TH-PPM UWB communication system.

Performance calibration of lineariser schemes designed to offset the impairments arising through high power amplifier (HPA) nonlinearities is addressed in this paper. Relating to the importance of linearisation in future reconfigurable ultra wideband (UW) mobile wireless communication systems, the benefits of the percentage linearisation area (PLA) measure is illustrated through EVM calculations ('simulation measurements') of an appropriate test signal after its passage through a typical HPA without linearisation and with varying degrees of linearisation.

Ultra wideband (UWB) communications systems provide high accuracy positioning estimation because the high multipath resolution capacity. This paper deals with the normalized minimum variance (NMV) technique for estimating time of arrival (TOA) exploiting the pulse train defined in the Impulse Radio (IR) transmission. Positioning estimation is tackled with the extended Kalman filter (EKF) with TOA bias tracking allowing high accuracy even in non line of sight (NLOS) scenarios.

Pulsed orthogonal frequency division multiplexing (pulsed-OFDM) is a simple frequency spreading technique that has been proposed to design low-complexity high performance multi-carrier ultra wideband (UWB) communication systems. A typical receiver for this system samples the received signal at Nyquist rate capturing all diversity branches. In this paper, we propose an alternate complexity-reduced receiver structure that uses analog to digital converters (ADC) with the sampling rate equal to a fraction of the Nyquist rate. We show that the output of the ADC in this case is a subset of the original diversity branches and contains complete information for all sub-carriers. Simulation results show that this technique outperforms the receiver with full rate sampling and selection diversity combining with considerable reduction in the complexity and power consumption. We also examine the possibility of enhancing the performance of the receiver by applying a subset selection algorithm based on the training sequences at the beginning of the every data packet. Simulation results in Rayleigh fading channel shows that the enhancement is negligible and we can adopt reduced-complexity receiver without selection algorithm.