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In this paper, we consider a two-way relay network, where multiple pairs of users exchange their information with the help of a multi-antenna relay station by means of two-way relaying. A relay processing scheme based on minimum mean square error (MMSE) criterion is employed at the relay station to suppress inter- and intra-pair interference. We formulate the optimization problem of minimizing the total transmit power of all users under the relay transmit power constraint and the given sum rate constraint. To solve the optimization problem and get the joint relay processing and power control policy, we propose an iteration algorithm. Simulation results show the performance of the proposed schemes and are coherent with what we expected.

In this paper, we deal with the multiple carrier frequency offsets (CFOs) estimation issues for orthogonal frequency-division multiple access (OFDMA) based uplink system. In such system, the interleaved carrier assignment scheme (CAS) has gained much attention for it brings maximum frequency diversity though it undergoes severe CFO problem than other schemes. The multiple-CFO estimation problem in this scheme uses a similar signal structure as that of Direction of Arrival (DOA) estimation problem in array signal processing, so subspace based multiple signal classification (MUSIC) algorithm can be exploited to estimate multiple CFOs. Compared with the conventional MUSIC algorithm utilizing eigenvalue decomposition of complex-value covariance matrix, the proposed unitary MUSIC and unitary root-MUSIC CFO estimation algorithms have comparable performance but lower computational complexity because of real-value covariance matrix used, which is verified by computer simulation.

In terms of the bidirectional relay networks with relay consisting of multiple antennas, we proposed the PNC detecting method at the relay node, which could generate the Likelihood Ratio (LLR) soft information directly for the XORed bit related to two access users. Following which the upper bound of the bit error performance is provided in a closed form. Simulation results demonstrate that the proposed closed-form expression could properly evaluate the system performance. Furthermore, the novel method could provide superior performance compared with the traditional network coding schemes based on MIMO detection, such as ZF or MMSE, and hereby the improved throughput could be achieved.

This paper proposes a novel cooperative power allocation (PA) scheme for multi-cell cellular systems employing distributed precoding which is designed by maximizing virtual signal-to-interference-and-noise ratio (VSINR) to suppress inter-cell interference. The base stations (BS) from all the cooperated cells serve all users within these cells. Each base station is assumed to know only channel state information (CSI) of its own users, meaning that BSs do not share CSI with each other. The proposed PA scheme is done by comparing channel gains with given thresholds. The channel whose gain is smaller than the threshold will be shut down, otherwise it will be allocated averagely among all BSs. Simulation results show that system with the proposed scheme performs better than that without BS cooperation. The proposed PA scheme offers another degree of freedom improving system capacity.

Cooperative relay networks have drawn more and more attention, since they can significantly improve network performance in terms of capacity and reliability. Multiple relay selection scheme is one of important issues which deserve careful design in such network. In this paper, we study the multiple relay selection (MRS) scheme in multiple parallel dual-hop Amplify-and-Forward relay networks, with the purpose of maximizing the received signal-to-noise ratio (SNR) at receiver, whereas the receiver adopts equal-gain combining technique. Based on general genetic algorithm (GA), an adaptive-GA (AGA) is proposed to approach optimal solution with better global and local search ability. Simulation results show that the proposed AGA can get almost optimal performance within much shorter time compared to exhaustive scheme.

In this paper, a novel General Flow Measurement Chip is implemented in Globalfoundries' 0.35um technology with the galaxy flow of Synopsys softwares. This novel chip consists of DW8051 IP core, I2C controller, MBIST controller, 256 Bytes SRAM, 512 Bytes SRAM and six universal ports. The external E2PROM is utilized for the chip to boot from and the external SRAM is utilized for the test platform. This SoC implementation procedure can be divided into three stages, which are front-end, back-end and verification respectively. Timing analysis is paid the most attention through this implementation. The layout and GDS II data are finished with timing convergence and no DRC, LVS violations. Finally, the test platform of this chip is given, using the Monitor-51 in Keil software to debug the objective programs step by step.

In this paper, a combined receiver for unitary space-time modulation (USTM) system is proposed, which combines the noncoherent detector and coherent detector for USTM constellations, thus called “combined receiver”. The output of the conventional noncoherent detector for USTM system is utilized to derive the channel measurement components which is then used to estimate the channel state information (CSI) using a Wiener filter based on minimum mean-square error (MMSE), and finally a coherent detector is employed. In our scheme, we can obtain not only the past and the present channel measurement components, but also the future ones, which are all used to estimate the CSI, resulting in a more refined channel estimation. Simulation results show the good performance of the proposed combined receiver compared with the previously proposed generalized quadratic receivers (GQRs).

Cognitive Radio (CR) is considered as one of the prominent techniques to improve the spectrum utilization by opportunistically sharing the radio spectrum resources with licensed users. This paper concentrates on characterizing the spectral-energy efficiency tradeoff in low and high signal-to-noise ratio (SNR) regimes for interference-tolerant CR networks under peak interference power constraints and in different fading environments. The analysis has been conducted under an assumption that perfect channel state information (CSI) of both primary and secondary receivers is available at the secondary transmitter. Our analysis proves that, in the low SNR regime, the minimum energy per bit required for reliable transmission is characterized by the supremum of the CR fading channel.

An assumption of the traditional layered protocol architecture is that all layers can be operated and optimized independently. Unfortunately, this assumption is not satisfied in wireless networks because wireless links introduce interdependence between physical (PHY) and upper layers. This paper investigates the impact of channel conditions on the performance of IEEE 802.11 DCF and proposes cross-layer optimization and design approach to improve the performance of DCF in fading channels. In this paper, a novel fade-induced packet error rate expressions based on fading statistics and error correction capability are developed. Based on these results, we propose a cross-layer analytical model to analyze the performance of IEEE 802.11 DCF in fading channels. The impact of channel conditions on the DCF performance is revealed.

This paper addresses a joint radio resource allocation (RRA) and scheduling problem in a multi-cell OFDMA network in which the backhaul capacity is constrained. The proposed scheme is pursuing both the network utility and fairness among all users in two different levels, the intracell level and the intercell level. Analysis and simulation results suggest the proposed scheme brings better performance for the cell edge users, and manages to build cooperation links between adjacent cells without extra signal overhead for the network.

A novel rectangular QAM nesting method for physical network coding is proposed for the broadcast phase in two-way relay networks, by which the asymmetric data rate transmission is achieved with a higher order modulation constellation carrying the higher data rate information while the lower data rate information carried by a sub-constellation nested in the higher order constellation. The novel nesting idea is implemented by two successive steps. Firstly the sub-constellations are constructed via Ungerboeck's set Partitioning (UP). Then we attempt to maximize the minimum distance between the signal points in each sub-constellation through changing the position of some signal points in a simple but effective way. And thereby, the optimized physical network coding is produced with improved BER performance and higher throughput. The results are clearly demonstrated by both theoretical analysis and simulation results.

The normal TCP congestion control has a problem that the sending rate in slow start phase changes so great that it leads to the decline of TCP performance due to the overflow of bottleneck link buffer. This paper analyzes the limitation of the normal TCP congestion control mechanism and proposes an improved algorithm of TCP congestion control with adaptive slow start based on the bandwidth measurement, namely ASS_TCP. We design a flexible slow start parameter model of adaptive parameter setting which adjusts the size of congestion window by the measurement of the end-to-end available bandwidth. Simulation results show that the probability of packet loss in the congestion window has been significantly decreased and TCP performance has been improved effectively.

In this paper, we propose a new concept called mobile Femtocell (MFemtocell) network, which can be considered as a practical implementation of mobile relays (more precisely, moving networks). MFemtocells can be deployed in moving vehicles, such as trains, buses, or private cars to provide enhanced user throughput, extended coverage, and reduction of the signaling overhead and drop calls. We investigate the spectral efficiency of cellular systems with MFemtocell deployment and two resource partitioning schemes. Simulation results demonstrate that with the deployment of MFemtocells, the spectral efficiency and average user throughput can significantly be increased while the signaling overhead is reduced.

In this paper, we investigate the closed loop extended orthogonal - space time block codes in decode-and-forward (DF) cooperative networks and propose an updatable Automatic Repeat reQuest (ARQ) protocol including relay selection. The relays correctly decoding the signals are incorporated into the relay set, and if there exist more than 4 relays in this set, we only choose 4 optimal relays based on the channel information. According to the number of the relays in the set, we bring forward a distributed EO-STBC method in the relay transmission to enhance the system performance. Simulation results prove that the proposed scheme can achieve better performance than the best relay and distributed-Alamouti scheme.