Design and analysis of LTE-WLAN wireless router with QOS preservation

Future wireless networks are envisioned to embrace a higher level of heterogeneity whereby different wireless technologies such as Long Term Evolution UMTS (LTE), Wireless Local Area Network (WLAN), WCDMA/HSPA, WiMAX, etc, not only will coexist but will also cooperate more closely. This is motivated by the fact that several complementary characteristics exist between these technologies. For example, one technology can be used as access technology while the other can be used for backhaul. To interconnect two or more wireless technologies, the usage of routing device is inevitable. In order to preserve the Quality of Service (QoS) across these technologies which come with different QoS definitions, a more comprehensive approach is required to preserve QoS across two diverse wireless technologies i.e. Enhanced Distributed Coordination Function (EDCA) for WLAN and Uplink/Downlink packet scheduling for LTE. WLAN is reasonably priced, easy to deploy and has been enjoying a wide market acceptance especially in the indoor. The LTE is expected to be the dominant 4G cellular technology. However it will take some time before LTE can attain the same level of adoption as what WLAN has achieved especially in the consumer market. The main objective of this research project is to design an access router that enables the interworking between WLAN and LTE with QoS preservation. First, the performance of both WLAN and LTE radio interfaces are investigated independently in terms of the data rates, user/system throughput, effect of multiple access and spectral efficiency. Next, different approaches and schemes which facilitate QoS preservation between WLAN and LTE over the router are investigated and evaluated in terms of different performance metrics (voice Mean Opinion Score, video delay, video traffic received, video jitter, video packet loss rate). The design and analysis of the performance are carried out through simulation as the only feasible approach to accomplish this work. OPNET Modeler is used to model the LTE-WLAN router as well as to perform the analysis. The results of this research verify the feasibility of the proposed router architecture and the interworking paradigm. The elegance of the proposed router implementation is that it does not require massive change in the existing wireless systems, LTE and WLAN to preserve the QoS. The results of the performance analysis show that it is crucial to have a QoS preservation mechanism in the router IP layer at any potential congestion point in the wireless network, to ensure that delay-sensitive and loss-sensitive applications, such as real-time video and voice, pass through unimpeded, relative to the loss-tolerant and delay-tolerant data applications. The comparison of the designed IP QoS preservation scheme namely, Priority Queuing without Block Acknowledgement (PQ noBA) shows that it can support 50% more multimedia application across the router than the other scheme

Delay-aware Link Scheduling and Routing in Wireless Mesh Networks

Resource allocation is a critical task in computer networks because of their capital-intensive nature. In this thesis we apply operations research tools and technologies to model, solve and analyze resource allocation problems in computer networks with real-time traffic. We first study Wireless Mesh Networks, addressing the problem of link scheduling with end-to-end delay constraints. Exploiting results obtained with the Network Calculus framework, we formulate the problem as an integer non-linear optimization problem. We show that the feasibility of a link schedule does depend on the aggregation framework. We also address the problem of jointly solving the routing and link scheduling problem optimally, taking into account end-to-end delay guarantees. We provide guidelines and heuristics. As a second contribution, we propose a time division approach in CSMA MAC protocols in the context of 802.11 WLANs. By grouping wireless clients and scheduling time slots to these groups, not only the delay of packet transmission can be decreased, but also the goodput of multiple WLANs can be largely increased. Finally, we address a resource allocation problem in wired networks for guaranteed-delay traffic engineering. We formulate and solve the problem under different latency models. Global optimization let feasible schedules to be computed with instances where local resource allocation schemes would fail. We show that this is the case even with a case-study network, and at surprisingly low average loads

Energy efficiency and traffic offloading in wireless mesh networks with delay bounds

In this paper, we study a wireless access network based on the Institute of Electrical and Electronics Engineers 802.11 standard and enriched with features such as caching and mesh networking. This system is analysed in terms of energy efficiency and traffic offloading, two objectives that are somewhat in contrast but both relevant to network and service providers as they directly impact the operational cost. In addition, QoS is also accounted for in the form of guaranteed bandwidth and bounded delay. To this aim, we developed a mathematical model of the system and solved it to optimality by means of integer linear programming. We can thus show how much can be saved both in terms of energy and traffic, also considering various tradeoff points among the two contrasting objectives. As a last step, we provide an investigation on the benefits of adding traffic aggregation features to the mathematical model