Methods and system for wireless networks with relays involving pseudo-random noise sequences
Methods and systems are provided for use with wireless networks having one or more cell in which each cell includes a base station (BS), at least one relay station (RS) and at least one mobile station (MS). The at least one relay station can be used as an intermediate station for providing communication between the BS and MS. Methods are provided for allocating OFDM resources for communicating between the BS, RS and/or MS for example dividing transmission resources into uplink and downlink transmissions and methods of inserting pilot symbols into transmission resources used by the RS. In some embodiments on the invention, the methods are consistent and/or can be used in conjunction with existing standards such as 802.16e.
1. A method for use in an orthogonal frequency division multiplexed (OFDM) communication system employing relay stations (RSs) comprising:
assigning a distinct pseudo-random noise (PN) sequence to each base station (BS) and each RS;
storing, in each RS, the distinct PN sequence for the respective RS;
generating, by each RS, a preamble based on the distinct PN sequence for the respective RS; and
transmitting by each RS, a signal to one of the BSs, the signal including the preamble corresponding to the respective RS.
2. The method of claim 1 wherein assigning the distinct PN sequence to each relay station comprises including assigned PN index, DL_PermBase, and PRBS_ID fields in management messages.
3. The method of claim 1 further comprising for purposes of routing, identifying each BS or RS by a BS identification (BS ID) in one of the management messages, wherein the one of the management messages is a media access control (MAC) management message.
4. The method of claim 3 wherein identifying each RS comprises assigning each RS a base station identifier (BS ID) in the management message.
5. The method of claim 1 wherein assigning a distinct PN sequence for a mobile relay station (MRS) is statically defined even when there is a handoff.
6. The method of claim 5 further comprising defining for mobile relay stations a system reserved sub-set of PN indexes so as to avoid collisions when a MRS moves across the network.
7. The method of claim 5 wherein the PN index is re-assigned during a handoff and further comprising informing any attached mobile stations (MSs) of the change and/or performing re-synchronization.
8. The method of claim 1 , further comprising:
modifying a management message to include the distinct PN sequence; and
identifying one of the respective RSs based on the management message.
9. A relay station configured to communicate via an orthogonal frequency division multiplexed (OFDM) communication system, comprising:
a memory; and
a processor configured to:
select one pseudo-random noise (PN) sequence from a plurality of PN sequences, wherein the one PN sequence is distinct from PN sequences assigned to other relay stations and base stations in a communication area of the relay station;
store the distinct PN sequence for the relay station in the memory
generate a preamble based on the distinct PN sequence for the relay station; and
transmit a signal to a base station, the signal including the preamble.
10. A base station configured to communicate via an orthogonal frequency division multiplexed (OFDM) communication system, comprising:
a memory; and
a processor configured to:
receive, from a relay station of the OFDM communication system, a list of a plurality of pseudo-random noise (PN) sequences for the relay station;
select one of the PN sequences from the list; and
assign the one of the PN sequences to the relay station, wherein the one of the PN sequences is distinct from PN sequences assigned to other relay stations and base stations in a communication area of the relay station.
11. The base station of claim 10 , further comprising:
a transmitter to transmit a management message to the relay station, the management message including the distinct PN sequence.