This paper considers a two-tier femto-macro overlay network architecture, where groups of femtocells are overlaid by macrocells. The capacity of the femtocells is limited, thus redirection of blocked femto calls to the overlaid macrocell is used as a QoS assurance strategy. Similar overflow approaches have been used in telephony; however, extension of this approach to capacity-constrained femto-macro overlay networks poses significant challenges due to the wide variety of bandwidth requirement of Internet services, the large number of femtocells overlaid by a macrocell, and the need for fast computations imposed by practical requirements of dynamic real-time resource allocation. We propose a new computationally efficient numerical method for the loss probability approximation in such two-tier femto-macro overlay networks. The accuracy of the method is verified by exact Markov-chain solutions for small systems and by simulations for larger systems.

Performance modeling is important for the purpose of developing efficient dimensioning tools for large complicated networks. But it is difficult to achieve in heterogeneous wireless networks, where different networks have different statistical characteristics in service and traffic models. Multiservice loss analysis based on multi-dimensional Markov chain becomes intractable in these networks due to intensive computations required. This paper focuses on performance modeling for heterogeneous wireless networks based on a hierarchical overlay infrastructure. A method based on decomposition of the correlated traffic is used to achieve an approximate performance modeling for multiservice in hierarchical heterogeneous wireless networks with overflow traffic. The accuracy of the approximate performance obtained by our proposed modeling is verified by simulations.

This paper studies loss calculation in hierarchical networks with multiservice overflows which have different call arrival rates, mean holding times, bandwidth requirements and share a common link. The loss calculation involves two challenging problems: 1) the computation of the two moment characterizations of multiservice overflow traffic over the shared link, 2) the calculation of the loss probabilities for multiservice non-Poisson overflow traffic in hierarchical systems. An efficient approximation method, known as multiservice overflow approximation (MOA), is proposed to enable multiservice networks designs with hierarchical architecture. Two contributions are included in the MOA method. First, an approximation based on blocking probabilities matching is proposed to compute the variances of multiservice overflows over the shared link. Second, a modified Fredericks & Hayward's approximation is used to calculate the loss probabilities of multiservice non-Poisson over flow traffic. The performance of the MOA method is evaluated in a two-tier hierarchical cellular network and compared with an existing approximation method based on multi-dimensional Markov-modulated Poisson process (MMPP). Verified by simulations, the MOA method achieves better accuracy in the general heterogeneous cases at lower computational cost than the MMPP method.

The recent investigations on interleave-division multiple-access (IDMA) have demonstrated its advantage in supporting high-data-rate and multi-rate services over wireless fading channels. This paper focuses on quality of service (QoS) guarantee in IDMA-based multi-service wireless networks. We propose a QoS architecture which addresses the key issues of QoS guarantee for multi-service in IDMA, including medium access control (MAC), admission control, power control, and rate allocation. The proposed IDMA QoS architecture avoids complex packet scheduling at the MAC layer which is however required in other existing multiple access systems. Data packets can be transmitted in IDMA without scheduling delay. Additionally, to improve the efficiency of random access, an interleave- division slotted-ALOHA (IDSA) access method is proposed for the IDMA MAC protocol. We derive the relationship between the arrival rate of access requests and the number of access interleavers allocated to an IDMA system for a given access success probability. Based on this relationship, we can adaptively adjust the number of access interleavers according to the traffic load of access requests, so as to ensure a satisfactory probability of successful access as well as low complexity of request detection at the receiver.

A novel hybrid ARQ (HARQ) scheme using a concatenated two-state trellis-coded modulation (CT-TCM) code is proposed for improving wireless TCP throughput. A distinguished feature of the proposed scheme is that the heavily punctured TCM codes are used for retransmissions of the corrupted data block, which are combined at the receiver with the previously received sequences of the same data block for decoding. By this method, significantly improved coding gain and efficient spectrum utilization can be achieved with very low complexity. A Markov model is developed to evaluate TCP throughput over the proposed HARQ in wireless link. By both analysis and simulation, we demonstrate that compared with other existing TCM-based ARQ schemes, significant improvement of TCP throughput over wireless links is achieved by the proposed CT-TCM HARQ while smaller buffer size is required at the access point.