Wireless communication technologies such as microwave radios are used to provide high-speed mobile backhaul connectivity for radio access networks in cases in which wire-based alternatives, e.g. cable or fiber, are not readily available and cannot be deployed in an economic or timely manner. Current mobile backhauls are predominantly deployed in tree or ring topologies, which simplify traffic management. Yet, with the increasing demand on backhaul capacity and the immense cost pressure on mobile backhaul solutions, meshed wireless mobile backhauls have been identified as a promising evolution. While traffic management in wireless mesh networks have been studied extensively in the literature, so far there is no quantitative analysis comparing the different topology options, i.e. mesh, ring and tree, regarding network performance and deployment cost. This paper fills this gap by studying the minimum cost problem of connecting a set of base station/gateway sites using different topologies while supporting both time- and space-varying traffic demands. Furthermore, we consider the additional constraint of resilience to single link failures. The evaluation results show that meshed wireless backhaul topologies are a cost-effective alternative to trees and rings, in particular in the face of spatial and temporal fluctuation of traffic demand and protection against link failures.

It is well-known that wireless links are error-prone and require retransmissions for recovering frames from errors and losses. Network coding (NC) has been proposed for more efficient MAC-layer retransmissions in WLANs. However, existing schemes employed the reception report mechanism, which is both inefficient and expensive. Furthermore, they considered neither fairness nor the effects of time-varying heterogeneous wireless networks. These issues are critical for achieving full benefit of network coding. Without addressing them, these schemes may even impair system performance. In this paper, a novel MAC-layer retransmission scheme, namely XOR rescue (XORR) is proposed. It estimates the reception status without extra overheads and devises a new coding metric, which accommodates the effects of the frames size and the channel condition. Finally, XORR employs NC-aware fair opportunistic scheduling, which is theoretically proven to be fair, i.e. not only the service time is evenly allocated, but also it always improves the expected goodput for every wireless station. It is further verified by theoretic analyses, extensive simulations and testbed experiments. Our results show that XORR outperforms the non-coding fair opportunistic scheduling and 802.11 by 25% and 40%, respectively.

Luby transform codes (LT) were originally designed for the binary erasure channel (BEC) encountered owing to randomly dropped packets in the statistical multiplexing aided Internet, where transmitted packets are not affected by the fading or noise of the environment. For the sake of transmitting data over the BEC routinely encountered in statistical multiplexing aided wireless Internet-style scenarios, LT codes have to be combined with classic channel codes. In this paper we introduce a novel almagamated LT coding and generalized low density parity check (G-LDPC) coding scheme. Upon exploiting the packet erasure information provided by the G-LDPC decoder for the LT decoder, the proposed scheme achieves a low bit error ratio (BER) for packet error ratio (PER) Eb/N0values in excess of 3.2 dB when transmitting data over the AWGN-BEC channel having a packet erasure probability of Pe=0.1. When communicating over the Rayleigh-BEC channel at Pe=0.1, an Eb/N0value of 5.3 dB was required. In comparison to the serially concatenated LT-GLDPC scheme using no information exchange between the G-LDPC decoder and the LT decoder, the amalgamated LT-GLDPC arrangement achieved an Eb/N0gain of up to 1.6-2.5 dB.

The pre-shared key based mechanisms for Transport Layer Security (TLS) were recently standardized by the IETF to extend the set of ciphersuites by utilizing existing key management infrastructures. The benefit of pre-shared based mechanisms is the avoidance or reduction of the cryptographic operations used in public-key based mechanisms. However, so far there are no performance measurements for pre-shared key based ciphersuites available. In this paper, we present a systematic analysis and performance comparison between the pre-shared key exchange mechanisms and the standard public key exchange mechanisms in TLS. Our performance metrics are processing time and transmitted amount of data for a handshake establishment. Furthermore, the interaction between the overall TLS handshake duration and the network environment is evaluated. The results for different key exchange mechanisms are comparatively studied and the design choices of pre-shared key based key exchange mechanisms have been validated. Experimental results give details about the performance improvement of the pre-shared key based mechanisms compared to the standard public key based mechanisms.

Classic low-density parity-check (LDPC) codes have recently been used as component codes in multilevel coding (MLC) due to their impressive BER performance as well as owing to their flexible coding rates. In this paper, we proposed a multilevel coding invoking generalized low-density parity-check (GLDPC) component codes, which is capable of outperforming the classic LDPC component codes at a reduced decoding latency, when communicating over AWGN and uncorrelated Rayleigh fading channels

An efficient symbol-flipping based decoding algorithm designed for nonbinary generalized low-density parity-check (GLDPC) codes is proposed. By extending the concept of the weighted bit flip voting (WBFV) algorithm designed for binary Hamming-code based GLDPC codes, the symbol-flipping decoding algorithm can be beneficially employed for decoding the family of GLDPC codes constructed from nonbinary constituent codes, such as nonbinary Bose Chaudhuri Hocquenghem (BCH) codes or Reed Solomon (R-S) codes. The simulation results demonstrate that improvements of 1 dB and 2.7 dB are achieved by the proposed coding scheme in comparison to the more conventional binary GLDPC codes using the WBFV decoding algorithm, when using the Galois Field GF(32) for communicating over AWGN and uncorrelated Rayleigh fading channels, respectively