Ch 11. Multiple Antenna Techniques for WMNs Myungchul Kim

–MAC protocol and network layer –How about physical layer ? Introduction

Multiple antennas –Smart antennas techniques –Multiple-input multiple-output (MIMO) Survey of multiple antenna techniques

–Multiple-input-single-output (MISO) BS: beamforming toward the direction of arrival (DOA) of the desired signal and antenna nulling to reduce the received power of the interference –The most interesting aspect of the MIMO systems lies in the multipath propagation. –MIMO provides gains Diversity gain: combat fading Spatial multiplexing gain: only by MIMO Survey of multiple antenna techniques

Beamforming and antenna nulling –The beamforming process will increase the power of the desired signal at the receiver side. –The antenna nulling could reduce the received interfering signal. –MISO Adaptive arrary and switched-beam Opportunistic or random beamforming Organized beamhopping (OBH) Diversity and space-time coding –The principle of diversity is to exploit the multiple fading paths between the transmitter and the receiver. –Space-time trellis codes (STTC) Survey of multiple antenna techniques

Spatial multiplexing –Utilize the parallel channels to transmit different data streams –Diagonal BLAST, vertical BLAST Survey of multiple antenna techniques

Characteristic aspects of WMNs 1.Self-organizing, self-roaming, and self-healing 2.Energy consumption 3.Coverage, connectivity, and reliablity due to multihop techniques cf. MANET, cellular networks 4.Open wireless architecture -Challenges in physical layer -Multiple interface -> multiple radio -> software-defined radio -MIMO: more than three times of capacity -Routing overhead: around 40% -Energy consumption at clients: multiple antenna -Cross-layer design and optimization: more hidden nodes in the directional antennas Overview of WMNs

Increase capacity and throughput –Multihop and MONWR -> directional antenna –Interference from concurrent transmission limits the max achievable capacity –Combining beam steering for tranmitting and adaptive beamforming for receiving, the capacity of the ad hoc networks with spatial time division multiple access (STDMA) could increase up to 980% when eight antenna elements are used for each node. –A mesh network testbed: 90% throughput improvement by using the directional antennas Improve routing performance –The transmission range of the desired signals could be greatly increased –Challenges: increased route discovery overhead, complicated MAC, and routing protocols Multiple antenna techniques for WMNs

Improve routing performance –Routing protocols suffer from long transmission delay and frequent link breakage at the intermediate nodes along a selected route –Energy-efficient routing protocol Multiple antenna techniques for WMNs

Increase energy efficiency –The best way to increase the energy efficiency is to use the directional antennas –The MANET with the directional antennas have not only higher throughput, but also higher energy efficiency –In order to utilize the directional antennas, effective algorithms, or MAC protocols are needed to enable nodes to point their antenna directions to the right place at the right time. Other performance improvement –Improved link quality -> better connectivity by 60% to 450% –QoS improvement: mainly at the MAC and above layers QoS aware protocol for the MANET with MIMO –Location estimation: up to 80% in static scenarios and up to 50% in mobie scenarios Multiple antenna techniques for WMNs

Other performance improvement –DSSS(direct sequence spread spectrum) ad hoc networks and WMNs for military purpose Multiple antenna techniques for WMNs