Boon Sain Yeo

Multi-Metric Gateway Discovery for MANET

Mobile ad hoc networks (MANETs) can be connected to the Internet via gateways to provide convenience of allowing mobile nodes in MANET to communicate with fixed nodes on the wired Internet. Current literature uses the number of physical hops to the gateway to decide which gateway the mobile node should connect to. However, gateway with shorter physical hops from mobile node may not necessarily be the ideal gateway, especially in a congested network with high channel contention. In this paper, physical hops, congestion level and contention level of route are combined as one single metric for gateway discovery. Using simulation, the performance of the combined metric for gateway discovery shows better performance compared to the current existing gateway discovery

An enhanced QoS routing algorithm for provision of end-to-end delay guarantee in low earth orbit satellite networks

Although several routing algorithms for LEO satellite networks have been proposed in the literature, the issue of providing guaranteed end-to-end delay bound QoS for with good throughput has not been solved. The motivation to design such an algorithm is based on the fact that LEO satellite networks are likely to play an important role in the future Internet. In this paper, weighted fair queuing (WFQ) is introduced into the LEO satellite system with the aim of providing end-to-end delay guarantees. High performance satellite routing (HPSR), which is able to provide a guaranteed end-to-end delay bound for LEO satellite networks with high throughput, is put forward. Unlike previously reported algorithms, HPSR applies a route computation algorithm which takes statistical multiplexing among connections into consideration, and which is able to obtain good system throughput. Through simulations on an Iridium-like constellation, the proposed approach is shown to achieve a guaranteed end-to-end delay bound with higher throughput as compared to a previously reported routing scheme.

A routing algorithm to provide end-to-end delay guarantee in low Earth orbit satellite networks

In this paper, the weighted fair queuing (WFQ) algorithm is introduced into a LEO satellite system with the aim of providing an end-to-end delay guarantee. A routing algorithm, i.e. satellite routing for end-to-end delay (SRED); which is able to provide a guaranteed end-to-end delay bound, is put forward. SRED includes a route computation algorithm in the presence of WFQ and an efficient partial rerouting algorithm that handles the dynamic nature of LEO satellites. Through simulations on an Iridium-like constellation, the proposed framework is shown to achieve a guaranteed end-to-end delay bound for admitted connections. The performance of SRED is dependent on the traffic characteristics of connections. Better performance is achieved when the connections have smaller packet size and burst size. SRED is shown to outperform the best effort scheme in system throughput whilst providing a delay bound service at the same time under certain traffic characteristics.

GREEN: a grid-based energy efficient probabilistic routing in wireless sensor networks

We propose a grid-based energy efficient probabilistic routing scheme for wireless sensor networks - GREEN. In this scheme, packets are forwarded through several possible routes, and intermediate nodes probabilistically forward or discard the packets. An individual node makes routing decisions using a routing algorithm, which is sensitive to the nodes physical location and its residual energy level. Simulation results show that such routing mechanism has high robustness in terms of packet delivery ratio even in harsh link conditions. Network planners have the flexibility to adjust some parameters to affect the routing decisions to adapt to a variety of network scenarios.

A multi-class services LEO satellite network

The increasing demand for a range of services with varying traffic flow characteristics, and the need for seamless wireless access, have led to a growing interest in multi-service low Earth orbit (LEO) satellite networks. A new approach to the problem of resource utilization is put forward. The approach divides the traffic into two classes, one associated with delay sensitive services, and the other with services that are not delay sensitive. An iterative algorithm is proposed which assigns traffic on a first-come-first-serve basis, subject to a maximum average packet delay constraint. The algorithm is shown to provide effective resource utilization when dealing with traffic having random time-varying characteristics.

The Use of Transport Model in Cellular Network Planning

Transportation planning has proven invaluable in urban planning. As a portion of the cellular traffic is generated by private and public transport passengers during their travels, it is therefore reasonable to argue that transport models can be used as the underlying platform to study the telecommunication traffic generated by this group of high mobility users. This paper looks into this aspect. An introduction on the four-step transport model with feedback is first given. Gravity model based on the maximization of entropy are used to generate the trip distribution. An example is given to illustrate how cell crossing rates can be obtained using the transport model and its usefulness in cellular network planning.

A Cell Planning Approach in Non-Isotropic Transmission Medium with the Capability of Supporting Cellular Networks Downsizing

Radio propagation model when used in cell planning is normally assumed to be isotropic over the whole area under consideration. However, in practice, making such an assumption is idealistic since the environment and terrains are unlikely to be the same in all directions. In this paper, a heuristic approach to perform cell planning with the isotropic transmission medium assumption removed is first presented. Since the deployment of 3G networks will reduce the number of 2G GSM subscribers, we next look into a simple economic model to achieve efficient design of downsized 2G cellular networks. We show how our proposed cell planning algorithm is useful in limiting the search space to obtain the new optimal base station configuration.

More Results on the Validation of Gravity Model and the Effect of User Mobility in Cell Planning

Gravity model has recently proposed for use to predict the movement of cellular mobile subscribers. In this paper, additional data are collected and similar validation process is performed to further our investigation. The results also verify that Gravity model can be used to predict user movements accurately, with the exception that the computed number of trips needs to be scaled by a factor ranging from 0.98 to 0.99. The impact of user mobility on cell planning is then discussed. The optimal design can be obtained through performing multi-period joint optimization.

Cell Capacity of CDMA Networks Taking the Effect of Mobile Locations into Consideration

In this paper, we evaluate the cell capacity of CDMA networks more accurately through simulation. Earlier work relating to the computation of Erlang cell capacity, other-cell interference imposed by an inter-cell mobile on the base station receiver is taken as the average with reference to all its possible spatial locations. This conventional approach implicitly is assuming that each inter-cell mobile has the same impact on the receiver performance. However, for interference-limited systems, mobiles located differently over the area will generate different amount of total other-cell interference, and hence, the receiver performance is expected to vary with instantaneous mobile locations. To investigate this effect, we first generate the mobile locations in all co-channel cells according to the known spatial distribution statistics. Perfect power control is applied to obtain the maximum number of mobiles in the referenced cell. By repeating for a large number of snapshots, the probability mass function for the maximum number of mobiles, which can be supported by the referenced cell, can be obtained to derive the Erlang cell capacity. Our results show that the Erlang cell capacity obtained using the conventional approach is smaller than that obtained from simulation, and unable to predict the variation in the maximum number of mobiles that can be supported by the referenced cell. We put forward an approach in quantifying the impact of mobile locations on the cell capacity without affecting the existing analytical approaches used in evaluating the Erlang cell capacity. Such an approach more accurately reflects the impact of mobile locations

Multi-Periods Optimization Strategy for Wireless Network Deployment

The deployment of wireless networks needs to consider both the cost and system performance metrics. The design objective is to decide the optimal placement of access points (or base stations) and to assign the available radio resources to respective traffic demand points with guaranteed performance, while keeping the deployment cost at its minimum. However, we feel that it would be better to adopt a design which can achieve long-term optimal rather than just at the instant of deployment. This paper set up a platform to look into the deployment of wireless networks which is able to optimize the profit generated over multiple periods each with different spatial traffic demands. Given a set of candidate sites, we first derive the placement and compute the transmission power of the access points to support a given spatial traffic demand over a specific period of time. The problem was formulated using a mixed integer linear programming model. Adjustable transmission range is made possible through power control to minimize the amount of interference among neighboring access points. With the knowledge on the projected demand traffic in subsequent periods, algorithms to maximize the long term profit are developed, both when the projected traffic are probabilistic and deterministic.