Performance Analysis and Improvement of WPAN MAC for Home Networks

The wireless personal area network (WPAN) is an emerging wireless technology for future short range indoor and outdoor communication applications. The IEEE 802.15.3 medium access control (MAC) is proposed to coordinate the access to the wireless medium among the competing devices, especially for short range and high data rate applications in home networks. In this paper we use analytical modeling to study the performance analysis of WPAN (IEEE 802.15.3) MAC in terms of throughput, efficient bandwidth utilization, and delay with various ACK policies under error channel condition. This allows us to introduce a K-Dly-ACK-AGG policy, payload size adjustment mechanism, and Improved Backoff algorithm to improve the performance of the WPAN MAC. Performance evaluation results demonstrate the impact of our improvements on network capacity. Moreover, these results can be very useful to WPAN application designers and protocol architects to easily and correctly implement WPAN for home networking

Performance enhancements for single hop and multi-hop meshed high data rate wireless personal area networks

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.The High Data Rate (HDR) Wireless Personal Area Networks (WPANs) typically have a limited operating range and are intended to support demanding multi-media applications at high data rates. In order to extend the communication range, HDR WPANs can operate in a wireless mesh configuration (i.e. enable multiple WPAN clusters) to communicate in a multi-hop fashion. HDR WPANs face several research challenges and some of the open key issues are limited capacity, optimum resource allocation to requesting devices and maintaining Quality of Service (QoS) for real time multimedia flows. Although, there have been some scheduling algorithms proposed for HDR WPANs, the main objective is to maintain the QoS in most cases whereas efficient and fair utilization of network capacity is still largely open for research. This thesis mainly intends to resolve the issues related to capacity of HDR WPANs such as admission control, fair allocation of Channel Time Allocations (CTAs), improvement in capacity through transmission power control, and efficient utilization of time by each flow. A technique which re-orders the time slots to reduce queuing delay for meshed WPANs is also proposed and evaluated. The first contribution aims to improve peer-to-peer connectivity in case of two or more independent piconet devices by proposing an inter-PAN communication framework that is augmented by an admission control strategy to handle the cases when the superframe capacity is congested. The queued devices are prioritized by proposing a parameter called the Rejection Ratio. The second contribution consists of a resource allocation framework for meshed WPANs. The main objectives are to reduce the control traffic due to high volume of channel time reservation requests and introduce an element of fairness in the channel time allocated to requesting devices. The objectives are achieved by using traffic prediction techniques and an estimated backoff procedure to reduce control traffic, and define different policies based on offered traffic for fair allocation of channel time. The centralized scheme uses traffic prediction techniques to use the proposed concept of bulk reservations. Based on the bulk reservations and resource allocation policies, the overall overhead is reduced while an element of fairness is shown to be maintained for certain scenarios. In the third contribution, the concepts of Time Efficiency and CTA switching are introduced to improve communication efficiency and utilization of superframe capacity in meshed WPANs. Two metrics known as Switched Time Slot (STS) and Switched Time Slot with Re-ordering (STS-R) are proposed which aim to achieve the purpose. The final contribution proposes and evaluates a technique called CTA overlappnig to improve capacity in single hop and meshed WPANs using tramission power control. Extensive simulation studies are performed to analyze and to evaluate the proposed techniques. Simulation results demonstrate significant improvements in meshed WPANs performance in terms of capacity utilization, improvement in fairness index for CTA allocation by upto 62% in some cases, reduction in control traffic overhead by upto 70% and reduction in delay for real time flows by more than 10% in some cases

About the Use of Adaptive Antennas in 60 GHz UWB-OFDM Personal Area Network Transceivers

The recent opening of unlicensed spectrum around 60 GHz has raised the interest in designing gigabit Wireless Personal Area Networks (WPANs). Since at 60 GHz the signal attenuation is strong, this band is basically suitable for short range wireless communications. It is understood that directional antennas can be employed to compensate for the path loss and combat the waste of power due to the scatter phenomena characteristic of these high frequencies. This thesis studies the use of adaptive array systems in 60 GHz Ultra Wide Band-Orthogonal Frequency Division Multiplexing (UWB-OFDM) personal area network transceivers. The study has been conducted by simulations and theoretical analysis. Two sensor arrangements have been considered, the Uniform Linear Arrays (ULA) and the Uniform Circular Arrays (UCA), in the simple case of the Line of Sight (LOS) transmission scenario. On the one hand we have designed a IEEE 802.15.3c Medium Access Control (MAC) phased-array controller throughput using Direction of Arrival (DOA) estimation to perform beamsteering. We have simulated the MAC controller with the network simulator ns-2. The impact of the array controller performance onto the achievable throughput of the wireless links has been studied to draw the requirements about the standard deviation of the DOA estimator. On the other hand, we have found the Cramér-Rao Bound (CRB) for DOA estimation of impinging 60 GHz OFDM sources. The requirements of the standard deviation of the DOA estimator are analysed against the CRB for DOA to validate the design of the directional 60 GHz UWB-OFDM transceivers. The comparison reveals that directional 60 GHz UWB-OFDM transceivers can achieve high wireless throughput with a number of pilot subcarriers and for a Signal to Noise Ratio (SNR) operating range typical of next generation WPAN

SPACE-TIME BEHAVIOR OF MILLIMETER WAVE CHANNEL AND DIRECTIONAL MEDIUM ACCESS CONTROL

An appropriate channel model is required to evaluate the performance of different physical (PHY) layer designs. However, there is no known space-time millimeter wave channel model that could benefit the use of directional antennas that is applicable in environments with lots of reflections such as residential or office. The millimeter wave signal strength is subject to temporal and spatial variations. The focus of the first part is the investigation of the characteristics of the millimeter wave propagation model. By analyzing measurement data of millimeter wave channels for indoor environments, space-time clusters are identified, and intercluster statistics for millimeter wave propagation are calculated. Correlation of the identified space-time clusters to the propagation environment is determined. In the second part, the effectiveness of the ray-tracing method in creating channel realizations in the intercluster and intracluster levels for millimeter wave indoor environments is validated. In the third part, a protocol to establish an optimal directional link between two nodes equipped with directional antennas is presented. The correctness of the protocol for different scenarios is illustrated using a ray-tracing tool. Then in the forth part, a Directional MAC (D-MAC) for supporting millimeter wave technology exploiting directional antennas is presented. The D-MAC is compatible with the current IEEE 802.15 MAC of WPAN, and it has backward compatibility to support devices which are not equipped with directional antennas. Finally, a directional neighbor discovery algorithm is presented which does not require time synchronization or any location information of communicating nodes. This means two nodes equipped with directional antennas can discover and communicate with each other through an established directional link as part of the D-MAC

Design and Analysis of Medium Access Control Protocols for Broadband Wireless Networks

The next-generation wireless networks are expected to integrate diverse network architectures and various wireless access technologies to provide a robust solution for ubiquitous broadband wireless access, such as wireless local area networks (WLANs), Ultra-Wideband (UWB), and millimeter-wave (mmWave) based wireless personal area networks (WPANs), etc. To enhance the spectral efficiency and link reliability, smart antenna systems have been proposed as a promising candidate for future broadband access networks. To effectively exploit the increased capabilities of the emerging wireless networks, the different network characteristics and the underlying physical layer features need to be considered in the medium access control (MAC) design, which plays a critical role in providing efficient and fair resource sharing among multiple users. In this thesis, we comprehensively investigate the MAC design in both single- and multi-hop broadband wireless networks, with and without infrastructure support. We first develop mathematical models to identify the performance bottlenecks and constraints in the design and operation of existing MAC. We then use a cross-layer approach to mitigate the identified bottleneck problems. Finally, by evaluating the performance of the proposed protocols with analytical models and extensive simulations, we determine the optimal protocol parameters to maximize the network performance. In specific, a generic analytical framework is developed for capacity study of an IEEE 802.11 WLAN in support of non-persistent asymmetric traffic flows. The analysis can be applied for effective admission control to guarantee the quality of service (QoS) performance of multimedia applications. As the access point (AP) becomes the bottleneck in an infrastructure based WLAN, we explore the multiple-input multiple-output (MIMO) capability in the future IEEE 802.11n WLANs and propose a MIMO-aware multi-user (MU) MAC. By exploiting the multi-user degree of freedom in a MIMO system to allow the AP to communicate with multiple users in the downlink simultaneously, the proposed MU MAC can minimize the AP-bottleneck effect and significantly improve the network capacity. Other enhanced MAC mechanisms, e.g., frame aggregation and bidirectional transmissions, are also studied. Furthermore, different from a narrowband system where simultaneous transmissions by nearby neighbors collide with each other, wideband system can support multiple concurrent transmissions if the multi-user interference can be properly managed. Taking advantage of the salient features of UWB and mmWave communications, we propose an exclusive region (ER) based MAC protocol to exploit the spatial multiplexing gain of centralized UWB and mmWave based wireless networks. Moreover, instead of studying the asymptotic capacity bounds of arbitrary networks which may be too loose to be useful in realistic networks, we derive the expected capacity or transport capacity of UWB and mmWave based networks with random topology. The analysis reveals the main factors affecting the network (transport) capacity, and how to determine the best protocol parameters to maximize the network capacity. In addition, due to limited transmission range, multi-hop relay is necessary to extend the communication coverage of UWB networks. A simple, scalable, and distributed UWB MAC protocol is crucial for efficiently utilizing the large bandwidth of UWB channels and enabling numerous new applications cost-effectively. To address this issue, we further design a distributed asynchronous ER based MAC for multi-hop UWB networks and derive the optimal ER size towards the maximum network throughput. The proposed MAC can significantly improve both network throughput and fairness performance, while the throughput and fairness are usually treated as a tradeoff in other MAC protocols

MAC layer implementation of the IEEE 802.15.3c standard

The transfer of data without wires is one of the main handicaps on this time. Not only for commercial reasons, also for research and manufacturing. The wireless technology on multimedia streaming has to evolve as fast as the multimedia technology does. Multimedia technology is evolving in order to reach better quality for the user's screen, therefore it needs more capabilities requirements; as better screens, better encoders, better devices to reproduce them. If we add the multimedia and the wireless technology, the result is that we need a wireless channel which could support the bandwidth that the video encoder needs. The uncompressed video or High Definition multimedia has entered so fast on the commercial issues. The main problem with that is the large amount of disk space that it needs, therefore the high rate transmission that require for streaming. To stand up to this with the wireless technology, the IEEE has developed the standard 802.15.3c in order to reach the data rate needed to transport the multimedia data without need wires. This standard is based on personal area networks (WPAN), which are computer networks used for communications between computer devices; including telephones, smartphones and tablets. Typically, a wireless personal area network uses some technology that permits communication within about 10 meters - in other words, a very short range. One such technology is Bluetooth. The WPANs could serve to interconnect all the ordinary computing and communicating devices that many people have on their desk or carry with them today. It is in its infancy and is undergoing rapid development. Proposed operating frequencies are around 2.4 GHz in digital modes. This standard uses the extremely high frequency of 60 GHz, it is considered between the highest radio frequency bands, from 30 to 300 GHz above which electromagnetic radiation is considered to be low (or far) infrared light. On this frequency band the rates could be greater than 5 Gbps, against the 2.5 Gbps that the uncompressed 1080p video, it is a good solution. The 60 GHz band usually requires line of sight between transmitter and receiver, and the 802.15.3c standard specification ameliorates this limitation through the use of "beam forming" at the receiver and transmitter antennas to increase the signal's effective radiated power. iii The aim of this bachelor thesis is to build a simulator of the 802.15.3c MAC layer protocol, in order to study the ways of the standard to construct a piconet, the structure of the channel time and the different modes to transmit data that is implemented on it. First of all, there is a summary of the main process of the standard to reach communication between two devices and an explanation of the MAC frames used for it. After that, I am going to talk about how is working the simulator and the results of it. Finally, the document is finished with conclusions and future works on the simulato