Abstract
The market for conventional first mile solutions (e.g., cable, fiber etc.) presents indeed high entrance barriers, and it is thus difficult for new operators to make their way into the field. This is due to the extremely high impact of labor-intensive tasks (i.e., digging up the streets, stringing cables etc.) that are required to put the necessary infrastructure in place. On the other hand, the market is experiencing an increasing demand for broadband multimedia services (Nokia, 2001), pushing towards the adoption of broadband access technologies. In such a situation, Broadband Wireless Access (BWA) represents an economically viable solution to provide Internet access to a large number of clients, thanks to its infrastructure-light architecture, which makes it easy to deploy services where and when it is needed. Furthermore, the adoption of ad hoc features, such as self-configuration capabilities in the Subscriber Stations (SSs) would make it possible to install customer premises equipment (CPE) without the intervention of a specialized technician, so boosting the economical attractiveness of WiMAX-based solutions. In this context, WiMAX is expected to be the key technology for enabling the delivery of high-speed services to the end users.
Key Terms in this Chapter
Hierarchical Scheduling: Semi-distributed scheduling approach in which some intelligence is moved from the central unit to the mobile stations in order to limit the MAC exchange overhead at the expense of increased complexity of the mobile equipment. This scheduling mechanism is expected to represent a valid base for designing an efficient QoS-enabled scheduler for WiMAX networks.
Mesh Architecture: Consists of several nodes, interconnected via wireless links where each node in the network cooperate to forward packets (by means of store-and-forward operations) to/from the Internet from/to the end node. A recent addition to the WiMAX standard is underway which will add full mesh networking capability.
Point-to-MultiPoint (PMP): Centralized architecture that serves a set of mobile stations within the same antenna sector in a broadcast manner. The PMP is the basic architecture for WiMAX networks.
Multiple-Input Multiple-Output (MIMO): Advanced communication architecture which takes advantage of multipath propagation, exploiting spatial degree of freedom in order to both increase throughput and reduce bit error rates. Such technology is expected to play a key role in boosting the performance of WiMAX systems.
Broadband Wireless Access (BWA): Technology aimed at providing high-speed wireless access to data networks. WiMAX is expected to be the leading broadband wireless access technology.
WiMAX: Acronym that stands for worldwide interoperability for microwave access, a certification mark for products that certify compatibility and interoperability of IEEE 802.16-compliant technologies.
Opportunistic Scheduling: Scheduling technique that exploits the time-varying nature and the spatial diversity of the wireless channel to make an effective use of the available system bandwidth. This approach is very suitable for WiMAX networks, at the cost of some additional complexity and signaling between PHY and MAC.