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The ability to discovery services is the major prerequisite for effective usability of MANETs. Broadcasting and caching service advertisements is an essential component in service discovery protocols for MANETs. To fully utilize the advantage of the cached service advertisements, the cached service description can be advertised with the local service description in a vicinity, which however will increase the size of service advertisement packets. A better solution is to using some aggregating method to reduce the packet size. In this paper, utilizing Bloom Filter as the aggregating method, we propose Bloom Filter Guided Service Discovery Protocol (BFGSDP) for MANETs. Two salient characteristics of BFGSDP are Bloom Filter Guiding scheme (BFG) and Broadcast Simulated Unicast (BSU). BFG scheme decreases the risk of flood storm problem by guiding request packets with bloom filters to those nodes with potential matched services. BSU scheme benefits from the broadcast nature of wireless transmissions by replacing multiple unicast request packets with one request packet transmitted in broadcast mode with all unicast receivers enclosed. Extensive simulations show that BFGSDP is a more effective, efficient, and prompt service discovery protocol for MANETs.

As a newly emerging technology with some inherent advantages over other wireless networks, wireless mesh networks (WMNs) have received much attention recently. In this paper, we present a cross-layer protocol design for WMNs, which combines the MIMO technique in the physical layer and the opportunistic medium access in the MAC layer into an integrated entity and jointly considers their interactions. In particular, we propose a protocol named opportunistic medium access control in MIMO WMNs (OMAC-MWMN). In an infrastructure/backbone WMN, mesh routers are grouped into clusters, in each of which a cluster head has multiple pending links with its neighbors. This traffic-driven clustering provides a great opportunity for a cluster head to locally coordinate the multiuser medium access. In each iteration of the scheduling, a cluster head opportunistically chooses some compatible neighbors among multiple candidates by utilizing the benefits of multiuser diversity. Then the cluster head simultaneously communicates with multiple selected compatible neighbors through multiuser spatial multiplexing. We formalize the problem of finding a scheduler for a cluster head to select compatible neighbors as finding a compatible pair with the maximum SINR (signal-to-interference and noise ratio) product. Our simulation results show that the proposed protocol can significantly improve system capacity with minimum extra overhead.

In this paper we present a method for determining optimal routes along selected paths in a wireless mesh network based on an interference aware delay analysis. We develop an analytic model that enables us to obtain closed form expressions for delay in terms of multipath routing variables. A flow deviation algorithm is used to derive the optimal flow over a given set of routes. The model takes into account the effects of neighbor interference and hidden terminals, and tools are provided to make it feasible for the performance analysis and optimization of large-scale networks. Numerical results are presented for different network topologies and compared with simulation studies.

In this paper we study load balancing in wireless mesh networks when the MAC layer of the network is modelled by STDMA. We formulate the linear problem for joint optimization of traffic allocation and transmission schedule. Both unconstrained path set, allowing arbitrary routing, and predefined paths are considered. In our numerical examples roughly third of the load of the most congested link can be reduced by load balancing. This reduction in the load decreases the delays of the network as well as increases the reliability of the system if link conditions change suddenly.

The purpose of this paper is to shed light on the accuracy of probabilistic delay bounds obtained with network calculus. In particular, by comparing calculus bounds with exact results in a series of M/M/1 queues with cross traffic, we show that reasonably accurate bounds are achieved when the percentage of cross traffic is low. We use recent results in network calculus and, in addition, propose novel bounds based on Doob’s maximal inequality for supermartingales. In the case of single M/M/1 and M/D/1 queues, our results improve existing bounds by when the utilization factor converges to one.

This paper presents a simple approximation to the delay distributions commonly used in traffic engineering and network planning. A key advantage of the approximation is its ability to estimate end-to-end delay without requiring convolutions or Laplace transforms. Two example applications to network planning are given: first, directly to the estimation of percentiles of end-to-end delay from component subnetwork measurements, and second, to network element characterization for computing delays in signaling or other systems that exhibit complex multiple message exchanges. A consideration of the accuracy of the method is included for both examples.

Many Internet applications employ multi-tier software architectures. The performance of such multi-tier Internet applications is typically measured by the end-to-end response times. Most of the earlier works in modeling the response times of such systems have limited their study to modeling the mean. However, since the user-perceived performance is highly influenced by the variability in response times, the variance of the response times is important as well.

We first develop a simple model for the end-to-end response times for multi-tiered Internet applications. We validate the model by real data from two large-scale applications that are widely deployed on the Internet. Second, we derive exact and approximate expressions for the mean and the variance, respectively, of the end-to-end response times. Extensive numerical validation shows that the approximations match very well with simulations. These observations make the results presented highly useful for capacity planning and performance prediction of large-scale multi-tiered Internet applications.

We investigate the end-to-end delay bounds in large scale networks with Differentiated services (DiffServ) architecture. It has been generally believed that networks with DiffServ architectures can guarantee the end-to-end delay for packets of the highest priority class, only in lightly utilized cases. We focus on tree networks with DiffServ architecture and obtain a closed formula for delay bounds for such networks. We further show that, in tree networks with DiffServ architecture, the delay bounds for highest priority packets exist regardless of the level of network utilization. These bounds are quadratically proportional to the maximum hop counts in heavily utilized networks; and are linearly proportional to the maximum hop counts in lightly utilized networks. We argue that based on these delay bounds DiffServ architecture is able to support real time applications even for a large tree network. Considering that tree networks, especially the Ethernet networks, are being adopted more than ever for access networks and for provider networks as well, this conclusion is quite encouraging for real-time applications. Throughout the paper we use Latency-Rate () server model, with which it has been proved that First In First Out (FIFO) and Strict Priority schedulers are servers to each in certain conditions.

We consider an asymmetric cyclic polling system with general service-time and switch-over time distributions with so-called two-stage gated service at each queue, an interleaving scheme that aims to enforce fairness among the different customer classes. For this model, we (1) obtain a pseudo-conservation law, (2) describe how the mean delay at each of the queues can be obtained recursively via the so-called Descendant Set Approach, and (3) present a closed-form expression for the expected delay at each of the queues when the load tends to unity (under proper heavy-traffic scalings), which is the main result of this paper. The results are strikingly simple and provide new insights into the behavior of two-stage polling systems, including several insensitivity properties of the asymptotic expected delay with respect to the system parameters. Moreover, the results provide insight in the delay-performance of two-stage gated polling compared to the classical one-stage gated service policies. The results show that the two-stage gated service policy indeed leads to better fairness compared to one-stage gated service, at the expense of a decrease in efficiency. Finally, the results also suggest simple and fast approximations for the expected delay in stable polling systems. Numerical experiments demonstrate that the approximations are highly accurate for moderately and heavily loaded systems.

For a broad class of polling models the evolution of the system at specific embedded polling instants is known to constitute a multi-type branching process (MTBP) with immigration. In this paper it is shown that for this class of polling models the vector that describes the state of the system at these polling instants satisfies the following heavy-traffic behavior, under mild assumptions: where is a known vector, (, ) has a gamma-distribution with known parameters and , and where is the load of the system. This general and powerful result is shown to lead to exact - and in many cases even closed-form - expressions for the Laplace-Stieltjes Transform (LST) of the complete asymptotic queue-length and waiting-time distributions for a broad class of branching-type polling models that includes many well-studied polling models policies as special cases. The results generalize and unify many known results on the waiting times in polling systems in heavy traffic, and moreover, lead to new exact results for classical polling models that have not been observed before. As an illustration of the usefulness of the results, we derive new closed-form expressions for the LST of the waiting-time distributions for models with a cyclic globally-gated polling regime. As a by-product, our results lead to a number of asymptotic insensitivity properties, providing new fundamental insights in the behavior of polling models.