Achievable Spectrum Efficiency Research Articles

Spectrum Co-existence of IEEE 802.11b and 802.16a Networks Using Reactive and Proactive Etiquette Policies

This paper presents an investigation of spectrum co-existence between IEEE 802.11b and 802.16a networks in the same shared frequency band using cognitive radio techniques with different levels of complexity. Simple reactive interference avoidance algorithms as well as proactive spectrum coordination policies based on etiquette protocols are proposed and compared in terms of achievable spectrum efficiency in a shared Wi-Fi/Wi-Max scenario. In reactive interference avoidance methods, radio nodes coordinate spectrum usage without exchange of explicit control information-this is done by adaptively adjusting transmit PHY parameters such as frequency, power and time occupancy based on local observations of the radio band. Because local observations provide information only about transmitters, they may not be sufficient for resolving spectrum contention in scenarios with "hidden receivers". Proactive coordination techniques solve the hidden-receiver problem by utilizing a common spectrum coordination channel (CSCC) for exchange of transmitter and receiver parameters. Radio nodes can cooperatively select key PHY-layer variables such as frequency and power by broadcasting messages in the CSCC channel and then following specified spectrum etiquette policies. An ns2 simulation model is developed to evaluate both reactive and proactive etiquette policies in scenarios with co-existing IEEE 802.11b and 802.16a networks. The density of radio nodes in the coverage region, and their degree of spatial clustering are key parameters in the system evaluation. Detailed simulation studies were carried out for a variety of scenarios including both single and multiple 802.11b hotspots per 802.16a cell with and without spatial clustering. Our results show that simple reactive algorithms can improve system throughput when sufficient "free space" (in frequency, power or time) is available for PHY adaptation. In more congested scenarios with spatially clustered nodes and hidden receivers, the proposed CSCC etiquette can significantly improve overall system performance over reactive schemes.

Applying the intelligent cell concept to PCS

We have concluded that the spectrum efficiency can be achieved in wireless PCS systems by applying the intelligent cell concept. The intelligent cell can either reduce interference by intelligently delivering the signal to the mobile unit, or can tolerate a great deal of interference while receiving with it. The former isolates the signal with multiple zones. In the latter, the signal resides with the interference but retains its processing gain. This paper presents the philosophy of achieving spectrum efficiency by applying the intelligent cell concept in wireless PCS systems.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Advanced Mobile Phone Service: Control Architecture

The cellular concept used in the Advanced Mobile Phone Service (amps) system to achieve spectrum efficiency requires a complex and flexible distributed system control architecture. Three major subsystems serve as the control elements: the mobile unit, the cell site, and the switching office. System control functions are partitioned among these subsystems to handle the following amps control challenges: interfacing with the nationwide switched telephone network, dialing from mobile units, supervising calls from mobile subscribers in the presence of noise and co-channel interference, performing call setup functions including paging and access, and locating and handing off mobiles between cell sites. This paper explains the techniques used to achieve the control functions of the three major subsystems and the ways they in turn participate in control of the total amps system.

Switching Plan for a Cellular Mobile Telephone System

Federal Communication Commission Docket 18 262 allocated a 75-MHz band to the common carriers to implement high capacity mobile telephone systems. The Bell System has proposed a cellular arrangement of low-power transmitters/receivers that permits frequency reuse in a coverage area. This method of achieving spectrum efficiency will require extensive centralized coordination and control to properly administer channel assignments and to interconnect the mobiles with each other and with the direct distance dialing (DDD) network. This can be accomplished by means of an electronic switching system (ESS) with special data terminals and trunking arrangements, and a unique program. In the proposed plan the radio sites (base stations) act effectively as remote concentrators in the frequency domain under the control of ESS, which in turn acts primarily as a trunk-to-trunk switcher. In addition to the usual switching, signaling, and supervising functions, the switching office must also perform numerous special functions including paging of mobiles, location of mobiles (signal strength and ranging data analysis), channel reassignment of mobiles, and reswitching of mobiles to various base stations-these last three occurring while customers are talking.

Switching plan for a cellular mobile telephone system

Federal Communication Commission Docket 18 262 allocated a 75-MHz band to the common carriers to implement high capacity mobile telephone systems. The Bell System has proposed a cellular arrangement of low-power transmitters/receivers that permits frequency reuse in a coverage area. This method of achieving spectrum efficiency will require extensive centralized coordination and control to properly administer channel assignments and to interconnect the mobiles with each other and with the direct distance dialing (DDD) network. This can be accomplished by means of an electronic switching system (ESS) with special data terminals and trunking arrangements, and a unique program. In the proposed plan the radio sites (base stations) act effectively as remote concentrators in the frequency domain under the control of ESS, which in turn acts primarily as a trunk-to-trunk switcher. In addition to the usual switching, signaling, and supervising functions, the switching office must also perform numerous special functions including paging of mobiles, location of mobiles (signal strength and ranging data analysis), channel reassignment of mobiles, and reswitching of mobiles to various base stations-these last three occurring while customers ate talking.