Wireless networks generally have a fixed amount of bandwidth available for information transmission. Schemes have been developed to allocate this bandwidth in the most efficient manner. Various bandwidth allocation schemes have been introduced in the cellular and satellite networks literature. For example, packet reservation multiple access (PRMA) has been introduced to integrate voice and data applications over the shared wireless medium. A major limitation of PRMA is its limited priority support for real-time traffic over non real-time traffic.
Time division multiple access (TDMA) is a well-known digital transmission technology that allows a number of users to access a single radio-frequency (RF) channel without interference by allocating unique time slots to each user. The time division multiple access (TDMA) based protocols proposed for wireless ATM networks were variations of Slotted Aloha and PRMA that do not provide any support for variations related to the priority of a particular class of traffic and are not optimal in any sense.
The wireless industry began to explore converting the existing analog network to digital as a means of improving capacity back in the late 1980s. In 1989, the Cellular Telecommunications Industry Association (CTIA) chose TDMA over Motorola's frequency division multiple access (FDMA) (today known as narrowband analog mobile-phone service [NAMPS]) narrowband standard as the technology of choice for existing 800 MHz cellular markets and for emerging 1.9-GHz markets. With the growing technology competition applied by Qualcomm in favor of code division multiple access (CDMA) and the realities of the European global system for mobile communications (GSM) standard, the CTIA decided to let carriers make their own technology selection.
The two major (competing) systems that split the RF are TDMA and CDMA. CDMA is a spread-spectrum technology that allows multiple frequencies to be used simultaneously. CDMA codes every digital packet it sends with a unique key. A CDMA receiver responds only to that key and can pick out and demodulate the associated signal.
Because of its adoption by the European standard GSM, the Japanese Digital Cellular (JDC), and North American Digital Cellular (NADC), TDMA and its variants are currently the technology of choice throughout the world. However, over the last few years, a debate has convulsed the wireless community over the respective merits of TDMA and CDMA.
The TDMA system is designed for use in a range of environments and situations, from hand-held portable use in a downtown office to a mobile user traveling at high speed on the freeway. The system also supports a variety of services for the end user, such as voice, data, fax, short message services, and broadcast messages. TDMA offers a flexible air interface, providing high performance with respect to capacity, coverage, and unlimited support of mobility and capability to handle different types of user needs. There exists a need for different services where TDMA doesn't differentiate. The next level of sophistication is differentiation.
In the article, “Dynamic Bandwidth Allocation for Multimedia Traffic in TDMA Broadband Satellite Networks”, by M. Hadjitheodosiou and E. Gerantiotis, in AIAA International Communications Satellite Systems Conference, Yokohama, Japan, February 1998, there was a proposal for a dynamic bandwidth allocation protocol for multimedia traffic with different levels of priority. The drawbacks of this protocol were twofold: the first drawback results from a lack of support for multiple classes of services with different levels of priority. The second drawback relates to the long-run optimization of the weighted sum of the distortion rate of video traffic, packet dropping probability of voice traffic, and the buffer lengths of data traffic. The authors asserted that solving the long-run optimization problem was found to be computationally intensive and hence, real-time implementation would prove to be infeasible in real-world situations.
In light of these shortcomings in the art, a need exists for a priority based resource reservation system which reserves resources based on a priority associated with requests for resource reservations. In the more specific case of a computer network, a need exists to provide a novel priority-based slot allocation strategy that gives an equal chance for all traffic streams to attempt reservations, and then leaves it for the allocation algorithm to make the optimal decision. It is further desirable to determine the optimal allocation on a frame-by-frame basis and to provide support for multiple classes of priority as well as providing a closed form solution.