Femtocells offer many advantages in wireless networks such as improved cell capacity and coverage in indoor areas. As these femtocells can be deployed in an ad-hoc manner by different consumers in the same frequency band, the femtocells can interfere with each other. To fully realize the potential of the femtocells, it is necessary to allocate resources to them in such a way that interference is mitigated. We propose a distributed resource allocation algorithm for femtocell networks that is modelled after link-state routing protocols. Resource Allocation using Link State Propagation (RALP) consists of a graph formation stage, where individual femtocells build a view of the network, and an allocation stage, where every femtocell executes an algorithm to assign OFDMA resources to all the femtocells in the network. Our evaluation shows that RALP performs better than existing femtocell resource allocation algorithms with respect to spatial reuse and satisfaction rate of required throughput.

Adaptive modulation and coding is an important characteristic of OFDMA based wireless networks. A group of subcarriers and symbols (which we refer to as “allocation unit”) can be assigned to an user equipment (UE) based on its channel conditions. The “allocation units” can have different bandwidths for different UEs depending on the current channel conditions of the UEs. The UEs typically have a minimum throughput requirement. In this article our goal is to design a scheduler that maximizes the number of scheduled UEs while meeting their minimum throughput requirements. First we define an analytical model for scheduling and then propose three algorithms for the optimization problem. We show that, given the sets of “allocation units”, maximizing the number of UEs is equivalent to finding the maximum independent set of a bounded degree graph. We also define the set allocation problem that minimizes the number of intersecting sets subject to certain constraints.

Growing popularity of high-speed wireless broadband access for real-time applications makes it increasingly relevant to study the admission control and scheduling of flows in a service differentiated manner. Next-generation wireless broadband networks employ orthogonal frequency division multiple access (OFDMA) technology that enables multiple users to communicate at the same time using a time-frequency grid. In this paper, we provide a mathematical model for prioritized admission control and scheduling in OFDMA-based multihop wireless networks. The problem is formulated as an integer linear program (ILP) that does joint admission control and scheduling of flows while satisfying its rate and latency requirements. We propose different heuristic algorithms for scheduling priority-based flows in centralized multihop OFDMA networks. We define the “Flow Admittance” (FA) metric and compare the different scheduling schemes based on this metric. Simulation results show that the Start from Frame Beginning (SFB) heuristic performs well in most of the scenarios. We also propose a combination approach that merges multiple heuristics. The FA values obtained from the combination approach are close to the ILP while incurring computation time orders of lower magnitude.

In this paper we propose an adaptive scheduling algorithm for IEEE 802.16j based wireless broadband networks. Computation of an optimal schedule for prioritized traffic in OFDMA based IEEE 802.16 wireless network is an NP-Hard problem. Hence, we propose a scheduling heuristic for an OFDMA based WiMAX relay network. The ORS (OFDMA Relay Scheduler) heuristic computes the zone boundaries (relay and access) in an uplink scheduling frame based on the number of RSs and MSs, the bandwidth demands and the link conditions. The ORS heuristic determines a schedule which assigns subchannels and timeslots to prioritized traffic based on the demand for various nodes while implementing frequency selectivity. The ORS adapts zone boundaries and the schedule to link and demand conditions at every scheduling period. We perform extensive simulations to demonstrate the effectiveness of adaptive zone scheduling and changes in rate conditions for various topologies.

Multi-hop WiMAX networks based on IEEE 802.16 has the potential of easily providing high-speed wireless broadband access to areas with little or no existing wired infrastructure. WiMAX technology can be used as "last mile" broadband connections to deliver streaming audio or video to clients. Thus, quality of service (QoS) is very important for WiMAX networks. Providing QoS in multi-hop WiMAX networks such as WiMAX mesh or mobile multi-hop relay networks is challenging as multiple links can interfere with each other if they are scheduled at the same time. We propose efficient heuristic algorithms for scheduling flows in a centrally scheduled multi-hop WiMAX network. The proposed algorithms guarantee bandwidth and delay constraints of flows and allow multiple non-interfering links to be scheduled at the same time. We also define a "schedule efficiency" metric for comparing different flow scheduling algorithms. The simulation results show that the "schedule flow subchannel" algorithm leads to the best schedule efficiency.