The broadcast storm becomes a very serious problem for ad hoc networks to migrate into the overlay networks for the application of group communications. The main concept of virtual subnet technology is the capability to group users into broadcast domains, which divides a virtual subnet into logic, instead of physical, segments and reduces the traffic overhead. With this characteristic, we propose a novel interoperability network model integrating a self-organizing ad hoc network and the Internet/a conventional network with the partition of physical/virtual subnets. Moreover, we describe a protocol to establish the virtual broadcast domains by using the IPv6 multicast-membership in ad hoc networks and perform IP-based network communications in a multi-switch backbone. Since the virtual subnet technology functions by logically segmenting the network into different broadcast domains, packets can only be delivered between fixed/mobile nodes with the same virtual identity. Therefore we can prevent the broadcast storm problem in MANET. The hierarchical networks, physical/virtual subnets, addressing method and mobility management are described, and some performance issues are evaluated.

To support real-time multimedia services in UMTS all-IP network, 3GPP TR 25.936 proposed two approaches to support real-time serving radio network controller (SRNC) switching, which require packet duplication during SRNC relocation. These approaches significantly consume extra system resources. This paper proposes the fast SRNC relocation (FSR) approach that does not duplicate packets. In FSR, a packet buffering mechanism is implemented to avoid packet loss at the target RNC. We propose an analytic model to investigate the performance of FSR. The numerical results show that packet loss at the source RNC can be ignored. Furthermore, the expected number of packets buffered at the target RNC is small, which does not prolong packet delay.

To support real-time multimedia services in UMTS all-IP network, Third-Generation Partnership Project TR 25.936 proposed two approaches to support real-time serving radio network controller (SRNC) switching, which require packet duplication during SRNC relocation. These approaches significantly consume extra system resources. This paper proposes the fast SRNC relocation (FSR) approach that does not duplicate packets. In FSR, a packet buffering mechanism is implemented to avoid packet loss at the target RNC. We propose an analytic model to investigate the performance of FSR. The numerical results show that packet loss at the source RNC can be ignored. Furthermore, the expected number of packets buffered at the target RNC is small, which does not prolong packet delay.

This paper proposes a radio channel assignment scheme called repacking on demand (RoD) for two-tier wireless local loop (WLL) networks. A two-tier WLL overlays a macrocell with several microcells. When a new call arrives at a two-tier WLL with RoD, if no idle channel is available in both the microcell and the macrocell, repacking is performed (i.e., a call in the macrocell is moved to its corresponding microcell), and then the reclaimed macrocell channel is used to serve the new call. An analytic model is proposed to compute the call blocking probability of the two-tier WLL with repacking. This analytic model is validated against simulation experiments. We prove that the blocking probability is not affected by the call holding time distributions, but is only dependent on the mean of the call holding times. Compared with some previous proposed schemes, RoD has low blocking probability and significantly reduces repacking rate.

In mobile telecommunications operation, radio channels are scarce resources and should be carefully assigned. One possibility is to deploy the hierarchical cellular network (HCN). We study a HCN channel assignment scheme called repacking on demand (RoD). RoD was originally proposed for wireless local loop networks. We expend this work to accommodate mobile HCN. A simulation model is proposed to study the performance of HCN with RoD and some previously proposed schemes. Our study quantitatively indicates that RoD may significantly outperform the previous proposed schemes.

This paper proposes an analytic model to compute the loss probability for wireless local loop (WLL) with a finite number of subscribers. The number of trunks between the WLL concentrator and the base station controller is less than the total number of radio links in the WLL. This model is validated against the simulation results. The execution of our model is efficient compared with simulation. However, its time complexity is higher than several existing analytic models that approximate the loss probability for WLL. Therefore, we design an efficient WLL network planning procedure (in terms of time complexity and accuracy) that utilizes the approximate analytic models to provide small ranges for selecting the values of system parameters. Our model is then used to accurately search the operation points of WLL within the small ranges of the system parameter values. This paper proves that the performance of WLL with limited trunk capacity and finite subscriber population is not affected by the call holding time distributions. Based on our model, we illustrate WLL design guidelines with several numerical examples.