Research in data broadcasting in a wireless network has addressed the problems of what to broadcast and how to schedule the broadcasts. However, it is still not clear whether a single broadcast for the entire network, or an individual broadcast for each wireless cell is should be prepared. Recently, we proposed the Broadcast Clouds (BC) technique that bunches together wireless cells based on a cost saving principle, and prepares a common broadcast for these. This would presumably reduce the bandwidth cost and increase the service provider’s profit. In this paper, we describe our simulation software, BCSIM, that we use to evaluate the performance of the BC approach, and present the results.

IEEE 802.11 MAC protocol PCF is intended to facilitate real time traffic, however, the performance of PCF is highly affected by conditions on the WLAN and it has unnecessary overhead. To address these problems, we propose an aging priority scheduling algorithm and a dynamic adaptation algorithm to vary the PCF interval based on the traffic and reduce the overhead. Simulation results show our algorithms are efficient and suitable for PCF traffic.

Transmit power control (TPC) protocols have been proposed to address the limited power supplies in ad hoc networks. However, most of the previous work minimizes the transmit power without considering both the energy wasted in collisions and the energy used to overcome the interference from all the interfering nodes existing in the network. Our previous work shows the optimal transmit power for the maximum throughput and per frame minimum consumed energy exists and occurs when the power level is sufficient to avoid the interference, and causes the least contention between nodes. In this paper, we propose a novel per-frame-based TPC protocol, DEM AC, in ad hoc networks using IEEE 802.11 at low PHY rate. To avoid interference, improve throughput, and save energy, DEMAC adaptively looks for the optimal transmit power based on the network interference and data payload. DEMAC is validated via simulations and is shown to outperform several existing TPC protocols

802.1x is a security protocol based on the frame structure of 802.11. It attempts to provide strong authentication, access control, and WEP (wired equivalent privacy) key management for wireless LANs. Unfortunately, 802.1x misses its goals in access control denial-of-service attacks. Currently, there are no IEEE approved ways to solve this security hole. We propose a central manager, not only to take the responsibility of an authentication server, but also to add functionality to prevent denial of service attacks. We also analyze how the 802.11 MAC layer protocol works with our solution.

Existing broadcasting techniques prepare a data broadcast by appending individual information items together, and send the data broadcast to a common channel from which all the mobile clients download. These techniques, however, fail to elaborate on how to construct the network perimeter within which to send their broadcasts. It is conceivable that these techniques use one of the following approaches: 1. a single broadcast for the entire network is prepared (one-for-all), 2. an individual broadcast for each wireless cell is prepared (one-for-each). In this paper, we explore the performance of both approaches via simulations. Particularly when the data items have locality, i.e., the increased likelihood of being requested at certain geographical areas, we suspect that these approaches have little use. For example, the traffic on a busy intersection might be requested very frequently within 10 miles of that intersection, and is of very little interest to those travelling 100 miles from that area. Hence, with a broadcast protocol that does not consider locality of data items, many clients will receive irrelevant data items.

This paper addresses the problem of providing secure access control in broadcast schemes in a wireless network. We consider an environment where clients subscribe to information objects sent via a broadcast onto a wireless network. In this context, a client should only be able to access its objects of interest for its subscription period, and the security system used must not be easily broken. Existing data broadcasting approaches fail to perform well with increased client loads. In this paper, we propose to use the Drop Groups (DG) protocol, that uses a novel grouping criterion. We present the broadcast organization under DG, and demonstrate that our approach is scalable. We use simulation to compare the DG protocol with existing techniques.

Push-based information delivery technology is commonly expressed as a broadcast solution where the information is pushed to a channel where all receivers can tap into. In this context, prior work has explored how to broadcast and what to broadcast. However, one problem not addressed so far is providing secure access control in broadcast schemes. Furthermore, existing broadcast work does not consider a subscription-based access scheme which is conceivable for most commodities. In this paper, we present existing secure access control schemes and adapt them to the broadcasting scenario, and outline their limitations in this environment. We propose a new protocol, single encoding multiple decoding (SEMD), to handle secure access and subscription services for broadcast. The superior performance of SEMD is demonstrated via a a simulation study of existing protocols and our protocol in a mobile computing environment.

Mobile computing has the potential for managing information globally. Data management issues in mobile computing have received some attention in recent times, and the design of adaptive braodcast protocols has been posed as an important probllem. Such protocols are employed by database servers to decide on the content of bbroadcasts dynamically, in response to client mobility and demand patterns. In this paper we design such protocols and also propose efficient retrieval strategies that may be employed by clients to download information from broadcasts. The goal is to design cooperative strategies between server and client to provide access to information in such a way as to minimize energy expenditure by clients. We evaluate the performance of our protocols both analytically and through simulation.

Mobile computing has the potential for managing information globally. Data management issues in mobile computing have received some attention in recent times, and the design of adaptive broadcast protocols has been posed as an important problem. Such protocols are employed by database servers to decide on the content of broadcasts dynamically, in response to client mobility and demand patterns. In this paper we design such protocols and also propose efficient retrieval strategies that may be employed by clients to download information from broadcasts. The goal is to design cooperative strategies between server and client to provide access to information in such a way as to minimize energy expenditure by clients. We evaluate the performance of our protocols analytically.