On the Employment of SMI Beamforming for Cochannel Interference Mitigation in Digital Radio

On the Employment of SMI Beamforming for Cochannel Interference Mitigation in Digital Radio

Thomas Hunziker (University of Kassel, Germany)
DOI: 10.4018/978-1-59904-988-5.ch004
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Many common adaptive beamforming methods are based on a sample matrix inversion (SMI). The schemes can be applied in two ways. The sample covariance matrices are either computed over preambles, or the sample basis for the SMI and the target of the beamforming are identical. A vector space representation provides insight into the classic SMI-based beamforming variants, and enables elegant derivations of the well-known second-order statistical properties of the output signals. Moreover, the vector space representation is helpful in the definition of appropriate interfaces between beamfoming and soft-decision signal decoding in receivers aiming at adaptive cochannel interference mitigation. It turns out that the performance of standard receivers incorporating SMI-based beamforming on short signal intervals and decoding of BICM (bit-interleaved coded modulation) signals can be significantly improved by proper interface design.
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Cochannel interference (CCI) becomes a major performance limiting factor in today's growing variety and density of wireless links and networks. Cellular systems occupying licensed frequency bands may evade CCI by a smart channel reuse policy. But in emerging decentralized peer-to-peer networks an efficient management of the channel access with the guarantee of limited CCI is a complex task, especially if the peers have directional transmission and reception capabilities. And proactive interference control across different systems sharing an unlicensed band is even more difficult to realize. Receiver techniques aiming at reactive interference mitigation, on the other hand, do not require cooperation between transceivers or systems, and they are thus a more viable approach to limit outages in decentralized or heterogeneous networking scenarios.

Data streams are normally split up and conveyed in short frames from sender to receiver. In multi-hop networks the frames need to be lightweight in order to limit latency in links over multiple hops since the relaying peers can usually not receive and transmit simultaneously. Moreover, besides of the data frames a multitude of even shorter control frames conveying “Hello”, “Request/Clear to Transmit”, “Acknowledge” messages and others are exchanged. As a consequence, if a channel is shared without coordination the interference may fluctuate at a much higher rate than the actual channel gain does due to multipath fading. This necessitates interference mitigation techniques which can adapt to CCI characteristics within short signal periods.

Equipped with array antennas, receivers can suppress interference via beamforming, i.e., a weighting and combining of the signals from the multiple antennas. Classic beamforming methods include the minimum variance distortionless response (MVDR) beamformer, which maximizes the signal-to-interference-plus-noise ratio (SINR) under the constraint of undistorted desired signal, and the minimum mean squared error estimator. When the spatial signatures of the interfering signals are completely unknown, an adaptive beamforming becomes necessary. Many of the popular adaptive beamforming techniques, discussed in textbooks like (Monzingo et al, 1980; Van Trees, 2002), rely on an inversion of a sample covariance matrix (SCM). The methods presented in (Vorobyov et al, 2003; Feldman et al, 1994; Bell et al, 2000; Lorenz et al, 2005; Li et al, 2003) feature enhanced robustness to mismatches in the spatial signature of the desired signal and other uncertainties via a diagonal loading of the SCM or more elaborate arrangements. The properties of the output of classic SCM-based spatial filters are analyzed in (Richmond, 1996; Van Veen, 1991), exposing the performance degradation compared to ideal beamforming based on perfectly known CCI statistics.

Complete Chapter List

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Table of Contents
Jack H. Winters
Chen Sun, Jun Cheng, Takashi Ohira
Chapter 1
Constantin Siriteanu, Steven D. Blostein
This chapter unifies the principles and analyses of conventional signal processing algorithms for receive-side smart antennas, and compares their... Sample PDF
Eigencombining: A Unified Approach to Antenna Array Signal Processing
Chapter 2
Zhu Liang Yu, Meng Hwa Er, Wee Ser, Chen Huawei
In this chapter, we first review the background, basic principle and structure of adaptive beamformers. Since there are many robust adaptive... Sample PDF
Robust Adaptive Beamforming
Chapter 3
Sheng Chen
Adaptive beamforming is capable of separating user signals transmitted on the same carrier frequency, and thus provides a practical means of... Sample PDF
Adaptive Beamforming Assisted ReceiverAdaptive Beamforming
Chapter 4
Thomas Hunziker
Many common adaptive beamforming methods are based on a sample matrix inversion (SMI). The schemes can be applied in two ways. The sample covariance... Sample PDF
On the Employment of SMI Beamforming for Cochannel Interference Mitigation in Digital Radio
Chapter 5
Hideki Ochiai, Patrick Mitran, H. Vincent Poor, Vahid Tarokh
In wireless sensor networks, the sensor nodes are often randomly situated, and each node is likely to be equipped with a single antenna. If these... Sample PDF
Random Array Theory and Collaborative Beamforming
Chapter 6
W. H. Chin, C. Yuen
Space-time block coding is a way of introducing multiplexing and diversity gain in wireless systems equipped with multiple antennas. There are... Sample PDF
Advanced Space-Time Block Codes and Low Complexity Near Optimal Detection for Future Wireless Networks
Chapter 7
Xiang-Gen Xia, Genyuan Wang, Pingyi Fan
Modulated codes (MC) are error correction codes (ECC) defined on the complex field and therefore can be naturally combined with an intersymbol... Sample PDF
Space-Time Modulated Codes for MIMO Channels with Memory
Chapter 8
Javier Vía, Ignacio Santamaría, Jesús Ibáñez
This chapter analyzes the problem of blind channel estimation under Space-Time Block Coded transmissions. In particular, a new blind channel... Sample PDF
Blind Channel Estimation in Space-Time Block Coded Systems
Chapter 9
Chen Sun, Takashi Ohira, Makoto Taromaru, Nemai Chandra Karmakar, Akifumi Hirata
In this chapter, we describe a compact array antenna. Beamforming is achieved by tuning the load reactances at parasitic elements surrounding the... Sample PDF
Fast Beamforming of Compact Array Antenna
Chapter 10
Eddy Taillefer, Jun Cheng, Takashi Ohira
This chapter presents direction of arrival (DoA) estimation with a compact array antenna using methods based on reactance switching. The compact... Sample PDF
Direction of Arrival Estimation with Compact Array Antennas: A Reactance Switching Approach
Chapter 11
Santana Burintramart, Nuri Yilmazer, Tapan K. Sarkar, Magdalena Salazar-Palma
This chapter presents a concern regarding the nature of wireless communications using multiple antennas. Multi-antenna systems are mainly developed... Sample PDF
Physics of Multi-Antenna Communication Systems
Chapter 12
MIMO Beamforming  (pages 240-263)
Qinghua Li, Xintian Eddie Lin, Jianzhong ("Charlie") Zhang
Transmit beamforming improves the performance of multiple-input multiple-output antenna system (MIMO) by exploiting channel state information (CSI)... Sample PDF
MIMO Beamforming
Chapter 13
Biljana Badic, Jinho Choi
This chapter introduces joint beamforming (or precoding) and space-time coding for multiple input multiple output (MIMO) channels. First, we explain... Sample PDF
Joint Beamforming and Space-Time Coding for MIMO Channels
Chapter 14
Zhendong Zhou, Branka Vucetic
This chapter introduces the adaptive modulation and coding (AMC) as a practical means of approaching the high spectral efficiency theoretically... Sample PDF
Adaptive MIMO Systems with High Spectral Efficiency
Chapter 15
Joakim Jaldén, Björn Ottersten
This chapter takes a closer look at a class of MIMO detention methods, collectively referred to as relaxation detectors. These detectors provide... Sample PDF
Detection Based on Relaxation in MIMO Systems
Chapter 16
Wolfgang Utschick, Pedro Tejera, Christian Guthy, Gerhard Bauch
This chapter discusses four different optimization problems of practical importance for transmission in point to multipoint networks with a multiple... Sample PDF
Transmission in MIMO OFDM Point to Multipoint Networks
Chapter 17
Salman Durrani, Marek E. Bialkowski
This chapter discusses the use of smart antennas in Code Division Multiple Access (CDMA) systems. First, we give a brief overview of smart antenna... Sample PDF
Smart Antennas for Code Division Multiple Access Systems
Chapter 18
Aimin Sang, Guosen Yue, Xiaodong Wang, Mohammad Madihian
In this chapter, we consider a cellular downlink packet data system employing the space-time block coded (STBC) multiple- input-multiple-output... Sample PDF
Cross-Layer Performance of Scheduling and Power Control Schemes in Space-Time Block Coded Downlink Packet Systems
Chapter 19
Yimin Zhang, Xin Li, Moeness G. Amin
This chapter introduces the concept of multi-beam antenna (MBA) in mobile ad hoc networks and the recent advances in the research relevant to this... Sample PDF
Mobile Ad Hoc Networks Exploiting Multi-Beam Antennas
Chapter 20
Toru Hashimoto, Tomoyuki Aono
The technology of generating and sharing the key as the representative application of smart antennas is introduced. This scheme is based on the... Sample PDF
Key Generation System Using Smart Antenna
Chapter 21
Nemai Chandra Karmakar
Various smart antennas developed for automatic radio frequency identification (RFID) readers are presented. The main smart antennas types of RFID... Sample PDF
Smart Antennas for Automatic Radio Frequency Identification Readers
Chapter 22
Konstanty Bialkowski, Adam Postula, Amin Abbosh, Marek Bialkowski
This chapter introduces the concept of Multiple Input Multiple Output (MIMO) wireless communication system and the necessity to use a testbed to... Sample PDF
Field Programmable Gate Array Based Testbed for Investigating Multiple Input Multiple Output Signal Transmission in Indoor Environments
Chapter 23
Masahiro Watanabe, Sadao Obana, Takashi Watanabe
Recent studies on directional media access protocols (MACs) using smart antennas for wireless ad hoc networks have shown that directional MACs... Sample PDF
Ad Hoc Networks Testbed Using a Practice Smart Antenna with IEEE802.15.4 Wireless Modules
Chapter 24
Monthippa Uthansakul, Marek E. Bialkowski
This chapter introduces the alternative approach for wideband smart antenna in which the use of tapped-delay lines and frequency filters are... Sample PDF
Wideband Smart Antenna Avoiding Tapped-Delay Lines and Filters
Chapter 25
Jun Cheng, Eddy Taillefer, Takashi Ohira
Three working modes, omni-, sector and adaptive modes, for a compact array antenna are introduced. The compact array antenna is an electronically... Sample PDF
Omni-, Sector, and Adaptive Modes of Compact Array Antenna
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