Advanced Retransmission Protocols for Critical Wireless Communications

Advanced Retransmission Protocols for Critical Wireless Communications

Salima El Makhtari (Abdelmalek Essaadi University, Morocco), Mohamed Moussaoui (Abdelmalek Essaadi University, Morocco), Ahmed El Oualkadi (Abdelmalek Essaadi University, Morocco) and Hassan Samadi (Abdelmalek Essaadi University, Morocco)
DOI: 10.4018/978-1-5225-2113-6.ch011
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Abstract

This chapter provides background about Hybrid Automatic Repeat reQuest (HARQ) protocols. First, the critical situations that may be faced by wireless communication systems especially cellular mobile technologies in case of very noisy radio channels are introduced. Particularly, the chapter introduces the HARQ protocols, their main constituent components as well as some related application areas. Then, the state-of-the-art of HARQ protocols is presented. The next section explains the three basic ARQ protocols. Then, the different HARQ types are detailed. Then, a mathematical model of type II HARQ based on Rayleigh fading channel is provided. This analytical analysis is followed by a discussion of the throughput which is one of the most interesting metrics used to measure the performance of HARQ systems. The readers can find in the next section a description of the HARQ systems architecture where 3GPP LTE is used to illustrate and explain how such systems operate. Finally, the last section concludes the chapter.
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Introduction

In modern wireless communication systems, especially digital cellular mobile phone technologies, demands for high data rates and reliability are increasing dramatically. However, ensuring that the data transmitted at high speed, over noisy wireless channels, is correctly received by the end user becomes more and more challenging. In despite of the availability of different channel estimation models and methods, the errors induced in case of severe noise and fading remain critical and may cause great damage. Many solutions have been developed to deal with poor transmission channels quality. To illustrate: Forward Error Correction (FEC) codes, Adaptive Modulation and Coding (AMC), Automatic Repeat Request (ARQ) and Hybrid Automatic Repeat reQuest (HARQ).

This chapter provides information on HARQ protocols for readers. These solutions are a powerful type of feedback-based communications and play a key role in enhancing reliability of wireless transmission links. HARQ protocols are cross-layer techniques and the result of combining classical ARQ schemes, FEC codes and error detection techniques such as Cyclic Redundancy Check (CRC) in addition of packets soft combining solutions. They enable reliable communication and improve the throughput performance over time-varying fading channels by leveraging both FEC and ARQ to their high potential when used together and mitigating their individual drawbacks. HARQ protocols continue to attract the intensive attention of researchers and have been adopted by many wireless communication systems, particularly the most recent cellular mobile technologies like as IEEE 802.16m (Institute of Electrical and Electronics Engineers [IEEE], 2011), IEEE 802.16e (IEEE, 2006) and the most recent 3GPP cellular standards such as High Speed Downlink Packet Access (HSDPA) (Third Generation Partnership Project, 2009), Long Term Evolution (LTE) (Third Generation Partnership Project, 2008) and Long Term Evolution Advanced (LTE-A) (Third Generation Partnership Project, 2010).

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