SDMA

v  Spatial division multiple access (SDMA) is a channel access method used in mobile communication systems which reuses the same set of cell phone frequencies in a given service area. Two cells or two small regions can make use of the same set of frequencies if they are separated by an allowable distance (called the reuse distance).

v  Techopedia explains Spatial Division Multiple Access (SDMA)

v  SDMA increases the capacity of the system and transmission quality by focusing the signal into narrow transmission beams. Through the use of smart antennas with beams pointed at the direction of the mobile station, SDMA serves different users within the same region.

Mobile stations operating outside the bounds of these directed beams experience a near zero interference from other mobile stations operating under the same base station with the same radio frequency.

Since the beams are focused, the radio energy frequency can have increased base station range. This attribute of SDMA allows base stations to have larger radio coverage with less radiated energy. This narrow beam width also allows greater gain and clarity.

Under traditional mobile phone network systems, the base station radiates radio signals in all directions within the cell without knowledge of the location of the mobile station. SDMA technology channels radio signals based on the location of the mobile station. Through this method, the SDMA architecture saves on valuable network resources and prevents redundant signal transmission in areas where mobile devices are currently inactive.

The main advantage of SDMA is frequency reuse. Provided the reuse distance is preserved in the network architecture, interference can be near zero, even if mobile stations use the same allocated frequencies.

v  Wireless communication systems are genera.lly composed of one or more local central sites, herein "termed base stations, through which wireless transmitter/receivers gain access to a larger information network. Base stations service local areas wherein a number of wireless users, fixed or mobile, are located. The function of the base station is to relay messages to and from users all O\'er the network. In cellulal' mobile systems, for example, this task is performed by relaying messages to and receiving signals from a ~'Iobile Telephone Switching Office (~ITSO). A wireless user establishes a two-way (full-duplex) communication link with one or more other users also having some access to the network by first requesting access to the network through the local base station, This communication is accomplished in cellular mobile communications and wireless local area computer networks (LANs), for example, by suitably modulating electromagnetic waves. The same is true of the next generation Per·wnal Coml11unicaticn Systems (PCSs) to which this document is directed.

v  Current state-of-the-art requires that users transmit signals in different frequency channels, use different coding schemes in the same frequency channels, or be transmitted in non-overlapping time intel'vals fOl' the signals to be correctly received. SOMA is a. new technique for separating multiple messages in the same frequency, code, or time channel using the fact that they are in different spatial channels, Hereinafter, the term channel will be used to denote any of the con\'entional channels (frequency, time, code) or any combination thereof. The term spatial cllannelrefers to the new concept unique to SOMA. \Vireless communication is becoming an increasingly common form of communication, and the demand for such service continues to grow, Examples i;U operation today include cellular mobile communication networks, wireless telephone networks, cordless telephones, satellite communication networks.

v  wireless cable TV, multi-user paging systems, high-fr.equency (HF) modems, and more. The next generation PCS systems will be yet another addition to this list. Current implementations of these communication systems are all confined to limited frequcncy bands of operation either by practical considerations or, as is more often the casc, by go\'emment regulation, As the capacity of these systems has been reached, demand for more service has had to be met by allocating more frequency spectrum to the particular application along with attempts to utilize the allocated spectrum mOl'e efficiently.

v  In light of the basic physical principle that transmission of information requires bandwidth, the fundamelltallimitations of a finite amount of practically usable spectrum present a substantial barrier to meeting an exponentially increasing demand for wireless information transmission, Since, as has been demonstrated SECTION 2. THE SOMA CONCEPT over the last decade, the amount of rractica!ly usable frequency spectrum can not keep pace with t~e demand, there lS a critical need for new technology for increasing the abil· ity of such systems to transfer information. TillS document directly addresses this need and describes proprietary Spatial Communications, Inc. technology which is compatible with current as well as future modulation schemes and standards.