A novel routing and transmission protocol for wireless systems
Original Publication Date: 2001-Oct-01
Included in the Prior Art Database: 2003-Jul-23
Harald Haas: AUTHOR [+3]
This invention is in the field of self-organizing wire- less networks. It describes a routing protocol which, amongst other advantages, allows the joint exploitati- on of both, joint-detection (JD) and joint- transmission (JT). The main principle is that the same information is routed to mobile stations (MS) (prima- rily remotely located ones) via different paths. This routing protocol utilises the time-division duplex (TDD) mechanism (see fig. 1). The data on the mul- tiple transmission links is processed using the JT technique in order to achieve interference reduction at the receiver. In conventional systems that use JT several access points (AP) are connected via cables to a central unit (CU). This invention avoids extra cabling completely. The main idea is depicted below.
Information / Kommunikation
This example shows a set-up with a single base stati-on (BS1) and in total five MS’s (MS1 – MS5). Thenumbers on top of the arrows indicate the content forthe respective MS. For example, between BS1 andMS1 the information for MS1, MS2, MS4 and MS5is routed. This allows the exploitation of trunkinggain on these links. In this way the information to, forexample, MS5 is routed via three links (MS3-MS5,MS1-MS5 and MS4-MS5).
The advantages of the novel routing technique are:
• Joint transmission can be applied without therequirement of access points (AP) that would beconnected by wire or fibre optical cables. In thenetwork concept described in this invention, theMS’s themselves act as AP’s. For example, MS5is served by MS3, MS1 and MS4 (blue arrows).The signals are formed such that interference isavoided, given that the channel is known a pri-ori . A similar mechanism applies for MS4 (ar-rows connecting MS4 with BS1 and MS2).
• This novel scheme ensures that the farther a MSis located away from the BS, the greater thenumber of links are that serve this MS. Thismeans that if a single path is heavily shadowedthere are still ‘backup–links’ which ensure that ahigh level of signal power is maintained even forhigh distant mobiles, i.e. space diversity is inher-ently applied.
• This novel method exploits macro-diversity.
• The paths of the multiple transmissions encoun-ter a different number of hops. This means thatthe same data is transmitted with a different de-lay. This mechanism constitutes delay diversitywhich has recently appeared in literature in con-nection with space-time codes. In the exampleabove, MS4 is served by the BS1 directly, butalso via the path (BS1->MS1-> MS2) which in-troduces a threefold delay as compared with thedirect path.
• The novel approach allows the use of smart an-tennas more easily. This can be explained asfollows: at the BS1, for example, only threelinks have to be served as compared to 5 whenthe BS serves each MS individually.
• Ad–hoc networks where a link is routed via asingle MS have the following disadvantage: if aMS (hop) within a sequence of single hops isswitched off...