Quality of service design issues in multimedia communications over power line networks

Home Networking is one of the major hurdles in enabling ubiquitous data and multimedia distribution. Most houses are not equipped with specialized wiring for networking purposes and retrofitting them with new wiring is prohibitively expensive. Hence, the use of existing in-home power line infrastructure for networking purposes can go a long way towards solving the in-home connectivity problem.; In this dissertation we first investigate the viability of power line communications (PLC) by evaluating the performance of HomePlug 1.0. Detailed event based simulation models were used to show that HomePlug 1.0 can provide a maximum UDP and TCP data rates of 7.86Mbps and 5.90Mbps. Extensive field testing in 20 houses showed that HomePlug 1.0 provides an average of 2.3Mbps higher throughput compared to IEEE 802.11b.; While HomePlug 1.0 is good enough for data networking, it will not be able to support the newly emerging multimedia applications like audio and video streaming. We study three issues that the new generation PLC systems need to overcome to enable multimedia communications: (a) AC line cycle variation in noise, (b) Impulse noise, and (c) Beacon Loss.; We use channel characterization measurements on 72 channels to investigate the performance enhancements that can be achieved by using a channel adaptation mechanism that is synchronized to the AC line cycle. The results show that a 30% improvement in physical layer (PHY) data rates can be obtained by continuously adapting to the AC line cycle. A time slot based adaptation that is more suitable for practical systems provided an average of 10% improvement in MAC data rates.; To effectively overcome impulse noise, we propose a novel 2-level MAC framing mechanism that enables efficient retransmissions. Our simulations and analysis show that this mechanism provides linear degradation in performance even under high FEC Block errors. Further investigation of the effect of transmission overheads on efficiency showed that low data rate, low latency QoS applications can incur significant loss in efficiency under high FEC block errors. Hence, PLC channel adaptation should take into account the application QoS requirements to optimize the overall system capacity.; Due to the unreliable nature of the power line channels, beacon reception cannot always be guaranteed. We investigate various persistent scheduling approaches to mitigate beacon loss. Our analysis shows that using persistent current and preview schedules, or persistent preview schedules, up to 10% beacon loss can be tolerated with minimal impact on MAC efficiency and QoS.