Channel assignment and call admission control for spatial division multiple access communication systems

• US 5,886,988 A
• Filed: 12/31/1996
• Issued: 03/23/1999
• Est. Priority Date: 10/23/1996
• Status: Expired due to Term

• Current Assignee: Intel Corporation
• Original Assignee: ArrayComm LLC (Ygomi LLC)
• Inventors: Yun, Louis C., Ottersten, Bjorn E.
• Primary Examiner(s): VU, HUY DUY
• Application Number:
  US08/777,598
• Time in Patent Office: 812 Days
• Field of Search: 370/252, 370/276, 370/277, 370/310, 370/328, 370/329, 370/331, 370/332, 370/333, 370/334, 370/341, 370/431, 370/465, 370/468, 455/423, 455/424, 455/425, 455/434, 455/450, 455/451, 455/452, 455/453, 455/464, 455/509, 455/510, 455/63, 455/67.1, 455/507, 455/512, 455/513, 364/574, 364/572
• US Class Current: 370/329
• CPC Class Codes: H04B 7/0408 using two or more beams, i.e. beam diversity
• CPC Class Codes: H04B 7/0491 using two or more sectors, i.e. sector diversity
• CPC Class Codes: H04B 7/0617 for beam forming
• CPC Class Codes: H04B 7/0845 per branch equalization, e.g. by an FIR-filter or RAKE receiver per antenna branch rake receivers as such H04B1/7115
• CPC Class Codes: H04B 7/086 using weights depending on external parameters, e.g. direction of arrival [DOA], predetermined weights or beamforming
• CPC Class Codes: H04L 27/20 Modulator circuits; Transmitter circuits
• CPC Class Codes: H04W 16/14 Spectrum sharing arrangements between different networks
• CPC Class Codes: H04W 16/28 using beam steering
• CPC Class Codes: H04W 52/34 TPC management, i.e. sharing limited amount of power among users or channels or data types, e.g. cell loading
• CPC Class Codes: H04W 52/50 at the moment of starting communication in a multiple access environment
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management
• CPC Class Codes: H04W 72/02 Selection of wireless resources by user or terminal
• CPC Class Codes: H04W 72/044 based on the type of the allocated resource
• CPC Class Codes: H04W 72/046 the resource being in the space domain, e.g. beams
• CPC Class Codes: H04W 72/541 using the level of interference
• CPC Class Codes: H04W 74/00 Wireless channel access
• CPC Class Codes: H04W 76/10 Connection setup

Abstract

The methods for channel assignment and channel reassignment are suitable for SDMA systems that accommodate the dynamically adaptive spatial channel conditions and allow for more frequent reuse of conventional channels. Three methods for uplink channel assignment are described: a cost function method, a predictive method, and a hierarchical method. The cost function method computes a cost function for each conventional channel based on a weighted correlation matrix of spatial signatures (vectors) of active subscribers. A spatial channel is created for the selected conventional channel if it is in use. The predictive channel assignment method predicts the uplink received power and interference-plus-noise for each conventional channel. Either the conventional channel with the minimum interference-plus-noise level or the channel with the maximal SINR is selected and a spatial channel is also assigned if the selected channel is in use. The hierarchical method combines the cost function method and the cost function method. The downlink channel assignment method, when not constrained by the uplink channel assignment, assigns a conventional channel to a new connection by estimating the downlink interference-plus-noise level from a subscriber report, spatial signature and weight vector, and computing a predicted downlink received signal level. Three methods for call admission control include: a cost function method, a predictive method, and a load based channel assignment method.

Claims

1. A channel assignment method for use in a wireless communication system for establishing an uplink connection between a subscriber station requesting an uplink connection and a base station, and for reassigning an existing connection to a subscriber station, the base station including an array of antenna elements and SDMA processing means, the SDMA processing means enabling one or more subscriber stations to communicate on the uplink with the base station on the same conventional channel, each subscriber station communicating on the same conventional channel communicating on a spatial channel of said same conventional channel, the method comprising:

(a) for each conventional uplink channel, computing a cost according to a cost function that is indicative of the interference level that may be realized by assigning the subscriber station to the conventional uplink channel, the cost function being a function of spatial properties of the subscriber station for communicating with the base station; and

(b) assigning to the subscriber station one of the conventional uplink channels with a cost that is less than a prescribed cost threshold.

2. The method of claim 1 wherein the SDMA processing means enables more than one subscriber station to communicate on the uplink with the base station on the same conventional channel, the method further comprising the step of assigning a new spatial channel to the subscriber station on the assigned conventional channel if the assigned conventional channel is in use by the base station for communicating on the unlink with a second subscriber station on an existing spatial channel.

3. The method of claim 1 wherein the assigned conventional channel has a minimal cost.

4. The method of claim 1 wherein the SDMA processing means processes uplink signals from a particular subscriber station according to a set of uplink demultiplexing weights for that particular subscriber station, wherein the spatial properties are the elements of the uplink spatial signature of the subscriber station, and wherein the cost function is a quadratic function of the uplink spatial signature of the subscriber station.

5. The method of claim 4 wherein the cost function is a weighted quadratic function of the uplink spatial signature of the subscriber station.

6. The method of claim 5 wherein the cost function is weighted by a sample covariance matrix of the base station antenna array received vector signal for a conventional channel.

7. The method of claim 1 wherein the SDMA processing means processes a uplink signals from a particular subscriber station according to a set of uplink demultiplexing weights for that particular subscriber station, wherein the spatial properties are the elements of the uplink spatial signature of the subscriber station, and wherein the cost function, c_k, is computed as

8. The method of claim 7 wherein the sample covariance matrix, R_zz.sup.(k), is estimated as an average from the received signal vectors, z.sup.(k) (i), at the base station antenna array on conventional channel k, where i is a received signal vector sample index, as ##EQU11##

9. The method of claim 7 wherein the sample covariance matrix, R_zz.sup.(k),is estimated as

10. The method of claim 9 wherein R_nn.sup.(k ) is estimated as

11. The method of claim 1 wherein the cost function is based on at least one uplink received signal quality factor selected from the group consisting of a received uplink signal level, a signal-to-interference-plus-noise ratio, an interference-plus-noise level, an intermodulation noise level, and a crest factor.

12. A channel assignment method for use in a wireless communication system for establishing an uplink connection between a subscriber station requesting an uplink connection and a base station, and for reassigning an existing connection to a subscriber station, the base station including an array of antenna elements and SDMA processing means, the SDMA processing means enabling one or more subscriber stations to communicate on the uplink with the base station on the same conventional channel, each subscriber station communicating on the same conventional channel communicating on a spatial channel of said same conventional channel, the method comprising:

(a) for each conventional uplink channel, computing a predicted cost according to a cost function, the cost function for a particular conventional channel based on the predicted received signal quality on the particular conventional channel, the received signal quality on a conventional uplink channel predicted using a model of the wireless communication system for predicting signal quality based upon existing connections, the computing using spatial properties of the subscriber station for communicating with the base station; and

(b) assigning to the subscriber station one of the conventional uplink channels that has a predicted cost that is less than a prescribed cost level.

13. The method of claim 12 wherein the SDMA processing means enables more than one subscriber stations to communicate on the uplink with the base station on the same conventional channel, the method further comprising the step of assigning a new spatial channel to the subscriber station on the assigned conventional channel if the assigned conventional channel is in use by the base station for communicating on the uplink with a second subscriber station on an existing spatial channel.

14. The method of claim 12 wherein the predicted received signal quality is based on predicting an uplink interference-plus-noise level.

15. The method of claim 12 wherein the predicted received signal quality is based on predicting a received signal to interference-plus-noise ration (SINR).

16. The method of claim 12 wherein the prescribed cost level corresponds to a minimal acceptable received bit error rate.

17. The method of claim 12 wherein the assigned conventional uplink channel has a predicted minimal cost level.

18. The method of claim 12 wherein assigning step (b) further requires that the assigned conventional channel have a SINR level that is greater than a prescribed minimal value.

19. The method of claim 12 wherein the spatial properties are the elements of the uplink spatial signature of the subscriber station, and wherein step (a) for computing further comprises:

(i) updating a covariance matrix of received uplink signals, R_zz.sup.(k), representative of received uplink signals at the base station before assigning channel k by predicting an updated covariance matrix, R_zz.sup.(k), representative of received uplink signals that would result if the new subscriber were to be assigned to channel k, where R_zz.sup.(k) =R_zz.sup.(k) +a_k, r_ss.sup.(k) +a_k, a_k^*,a_k is the uplink spatial signature of the new subscriber on conventional channel k, and r_ss.sup.(k) is a scalar representative of the new subscriber transmitted power on conventional channel k; and

(ii) computing an uplink spatial demultiplexing weight vector, w_k^U, where w_k^U =(R_zz.sup.(k))^-1 a_k r_ss.sup.(k).

20. The method of claim 19 wherein the updated inverse covariance matrix, (R_zz.sup.(k))^-1, is obtained from the expression

21. The method of claim 12 wherein the spatial properties are the elements of the uplink spatial signature of the subscriber station, and wherein step (a) for computing the predicted uplink received signal quality level on channel k further comprises:

(iii) predicting uplink received signal power as S_k^U =|w_k^U* a_k |² r_ss.sup.(k) ;

(iv) predicting uplink interference-plus-noise power for the new subscriber as I_k^U =w_k^U* R_zz.sup.(k) w_k^U ; and

(v) predicting the uplink SINR for channel k as SINR_k =S_k^U /I_k^U where R_zz.sup.(k) is the sample covariance matrix of the base station antenna array response on conventional channel k, a_k is the uplink spatial signature of the new subscriber on conventional channel k, r_ss.sup.(k) is a scalar representative of the new subscriber transmitted power on conventional channel k, and w_k^U is the uplink spatial demultiplexing weight vector for channel k.

22. The method of claim 12 further comprising a constraint for only permitting assignment of a conventional channel if the assignment results in a predicted uplink SINR for all active subscribers using the conventional channel which exceeds a prescribed SINR level.

23. The method of claim 12 wherein the predicted cost is based on at least one set of predicted uplink received signal quality factors selected from the group consisting of received uplink signal levels, interference-plus-noise levels, intermodulation noise levels, and crest factor values.

24. A channel assignment method for use in a wireless communication system for establishing an uplink connection between a new subscriber station requesting an uplink connection and a base station, and for reassigning an existing connection to a subscriber station the base station including an array of antenna elements and SDMA processing means, the method comprising:

(a) computing a first cost for each conventional uplink channel according to a first cost function that is indicative of the uplink interference level that may be realized by assigning the new subscriber station to said each conventional uplink channel, the computing including using spatial properties of the subscriber station for communicating with the base station;

(b) selecting a subset of conventional uplink channels, the subset consisting of the conventional uplink channels with a first cost that is less than a prescribed first cost level;

(c) for each conventional uplink channel of the subset, computing a second cost according to a second cost function, the second cost function for a particular conventional channel based on the predicted received signal quality on the particular conventional channel, the received signal quality on a conventional uplink channel predicted using a model of the wireless communication system for predicting signal quality based upon existing connections; and

(d) assigning to the subscriber station one of the conventional uplink channels of the subset that has a second cost that is less than a prescribed second cost level.

25. The method of claim 24 wherein the SDMA processing means enables more than one subscriber stations to communicate on the uplink with the base station on the same conventional channel, each subscriber station communicating on the same conventional channel communicating on a different spatial channel of said same conventional channel, the method further comprising the step of assigning a new spatial channel to the subscriber station on the assigned conventional uplink channel if the assigned conventional uplink channel is in use by the base station for communicating on the uplink with a second subscriber station on an existing spatial channel.

26. The method of claim 24 wherein the prescribed first and second cost levels correspond to a prescribed maximal received uplink bit error rate level.

27. The method of claim 24 wherein step (d) of assigning further requires that the assigned conventional channel have a SINR level that is higher than a prescribed SINR level.

28. The method of claim 24, wherein the wireless communication system uses power control when establishing an uplink connection, and wherein in step d), a conventional uplink channel is selected for assignment that has a SINR level greater than a prescribed SINR level.

29. The method of claim 24 wherein is based on at least one set of uplink received signal quality factors selected from the following list:

received uplink signal power levels, interference-plus-noise levels, intermodulation noise levels, and crest factor values.

30. A channel assignment method for use in a wireless communication system for establishing a downlink connection between a base station and a subscriber station, the base station including an array of antenna elements and SDMA processing means, the SDMA processing means enabling the base station to communicate on the downlink with more than one subscriber station on the same conventional channel, each subscriber station on the same conventional channel being communicated to on a different spatial channel of said same conventional channel, the method comprising:

(a) estimating, at the base station, the downlink received interference-plus-noise level that would result for each existing conventional channel if the subscriber was assigned to a given conventional downlink channel;

(b) computing, at the base station, a cost for each existing conventional downlink channel using a prescribed cost function based on the estimated downlink received interference-plus-noise levels; and

(c) assigning, at the base station, the subscriber station to a conventional downlink channel that has a computed cost that is less than a prescribed value,

the method further comprising the step of assigning a spatial channel to the subscriber station on the assigned conventional downlink channel if the assigned conventional downlink channel is in use by the base station for communicating on the downlink with a second subscriber station on an existing spatial channel.

31. The method of claim 30 wherein assigning step (c) further comprises selecting a downlink channel that has a minimal computed cost.

32. The method of claim 30 wherein estimating step (a) further comprises:

(i) measuring, at the subscriber station, downlink received signal levels on each downlink channel and reporting the downlink received signal levels to the base station;

(ii) estimating, at the base station, the downlink received interference-plus-noise levels from the reported downlink signal levels of measuring step (i).

33. The method of claim 32 wherein measuring step (i) of estimating step (a) further comprises each subscriber station, when not actively engaged in a call, periodically measuring the downlink received signal level on each conventional channel and reporting the downlink received signal levels to the base station.

34. The method of claim 32 wherein the downlink received interference-plus-noise levels are estimated as being the reported downlink received signal levels.

35. A channel assignment method for use in a wireless communication system for establishing a downlink connection between a base station and a subscriber station, the base station including an array of antenna elements and SDMA processing means, the SDMA processing means processing a downlink signal for a particular subscriber station according to a set of downlink multiplexing weights for that particular subscriber station, the method comprising:

(a) estimating, at the base station, the downlink received interference-plus-noise level that would result for each existing conventional channel if the subscriber was assigned to a given conventional downlink channel;

(b) computing, at the base station, a cost for each existing conventional downlink channel using a prescribed cost function based on the estimated downlink received interference-plus-noise levels; and

(c) assigning, at the base station, a conventional downlink channel that has a computed cost that is less than a prescribed value,

wherein step (a) for estimating downlink received interference-plus-noise levels on each downlink channel comprises the following steps;

(i) adjusting, at the base station, each existing subscriber'"'"'s downlink multiplexing weights as if the new subscriber was assigned to a given conventional channel;

(ii) measuring, at the new subscriber station, the downlink received signal level on the given channel after step (i) and reporting the downlink received signal level to the base station;

(iii) predicting, at the base station, a downlink interference-plus-noise level from the downlink received signal level of step (ii); and

(iv) readjusting, at the base station, each existing subscriber'"'"'s downlink multiplexing weights as if the new subscriber was not assigned to the given conventional channel.

36. A channel assignment method for use in a wireless communication system for establishing a downlink connection between a base station and a subscriber station, the base station including an array of antenna elements and SDMA processing means, the method comprising:

(a) estimating, at the base station, the downlink received interference-plus-noise level that would result for each existing conventional channel if the subscriber was assigned to a given conventional downlink channel;

(b) computing, at the base station, a cost for each existing conventional downlink channel using a prescribed cost function based on the estimated downlink received interference-plus-noise levels; and

(d) assigning, at the base station, a conventional downlink channel that has a computed cost that is less than a prescribed value,

wherein step (a) for estimating a downlink received interference-plus-noise level, I_k, for each existing channel k comprises, modeling the downlink received interference-plus-noise level, I_k, as a sum of the noise contribution, N_k, and a predicted second interference signal level that would result if the new subscriber was to be assigned to channel k, estimating the noise contribution N_k as a signal level difference between a measured downlink received signal level, P_k, on channel k and a computed first interference signal level due to all base stations using channel k.

37. The method of claim 36 wherein the SDMA Processing means processes a downlink signal for a particular subscriber station according to a set of downlink multiplexing weights for that particular subscriber station, wherein each subscriber station has a downlink spatial signature, and wherein the computed first interference signal level is computed as ##EQU12## where W_k,j^D* =S_k,j A_k,j.sup.†

, S_k,j is a diagonal matrix of base station j transmitted signal amplitudes, A_k,j is a column-wise concatenated matrix of known downlink spatial signatures at base station j for the subscriber stations on conventional channel k, A_k,j.sup.†

represents the pseudoinverse of A_k,j, and a_k^D,j is the downlink spatial signature for the new subscriber station on conventional channel k from base station j.

38. The method of claim 36 wherein the SDMA processing means processes a downlink signal for a particular subscriber station according to a set of downlink multiplexing weights for that particular subscriber station, wherein each subscriber station has a downlink spatial signature, and wherein the predicted second interference signal level for channel k is computed as ##EQU13## where ##EQU14## †

represents a pseudoinverse operation, S_k,j is a diagonal matrix of transmit signal amplitudes, A_k,j is a column-wise concatenated matrix of known downlink spatial signatures for the subscriber stations on conventional channel k at base station j, a_k^D,j is a downlink spatial signature for conventional channel k from base station j for the new subscriber station on conventional channel k, and w^* is the bottom row of matrix Sk,j A_k,j a_k^D,j !.sup.†

.

39. A channel assignment method for use in a wireless communication system for establishing a downlink connection between a base station and a subscriber station, the base station including an array of antenna elements and SDMA processing means, the method comprising:

(a) estimating, at the base station, the downlink received interference-plus-noise level that would result for each existing conventional channel if the subscriber was assigned to a given conventional downlink channel;

(b) computing, at the base station, a cost for each existing conventional downlink channel using a prescribed cost function based on the estimated downlink received interference-plus-noise levels; and

(c) assigning, at the base station, a conventional downlink channel that has a computed cost that is less than a prescribed value, and further comprising a step for assigning a selected downlink conventional channel) only if it is expected to result in an acceptable downlink received signal quality for each active subscriber using the selected conventional channel based upon at least one downlink quality factor selected from a group consisting of;

predicted cost;

predicted total base station transmitter power;

predicted intermodulation distortion level;

predicted interference-plus-noise level; and

predicted signal to interference-plus-noise ratio.

40. The method of claim 39 wherein the predicted intermodulation distortion level is obtained by computing a crest factor for each downlink !conventional downlink channel, the crest factor value being indicative of an intermodulation distortion level that would result if a given conventional downlink channel were to be assigned.

41. A channel assignment method for use in a wireless communication system for establishing a downlink connection between a base station and a subscriber station, the base station including an array of antenna elements and SDMA processing means, the method comprising:

(a) estimating, at the base station, the downlink received SINR level that would result for each existing conventional channel if the subscriber station were to be assigned to a given conventional downlink channel, the estimating using spatial information of the new subscriber;

(b) computing, at the base station, a cost for each existing conventional downlink channel using a prescribed cost function based on the estimated downlink received SNR level; and

(c) assigning, at the base station, a downlink channel that has a computed cost that is less than a prescribed value,

the method further comprising the step of assigning a spatial channel to the subscriber station on the assigned conventional downlink channel if the communications system supports and the SDMA processing means enables communication on more than one spatial channel on the same conventional downlink channel, and if the assigned conventional downlink channel is in use by the base station for communicating on the downlink with a second subscriber station on an existing spatial channel.

42. The method of claim 41 wherein the SDMA processing means enables more than one subscriber stations to communicate on the downlink with the base station on the same conventional downlink channel, each subscriber station on the same conventional channel being communicated to on a different spatial channel of said same conventional channel, the method further comprising the step of assigning a new spatial channel to the subscriber station on the assigned conventional downlink channel if the assigned conventional downlink channel is in use by the base station for communicating on the downlink with a second subscriber station on an existing spatial channel.

43. The method of claim 41 wherein the SDMA processing means processes a downlink signal for a particular subscriber station according to a set of downlink multiplexing weights for that particular subscriber station, wherein each subscriber station has a downlink spatial signature, and wherein the prescribed cost function of computing step (b) is based on SINR_k^D, an estimated downlink signal to interference-plus-noise ratio for each channel k, where SINR_k^D =S_k^D /I_k^D, S_k^D =|w_k^D* a_k^D |², w_k^D is the downlink multiplexing weight for the new subscriber on channel k, a_k ^D is the downlink spatial signature of the new subscriber on channel k, and I_k^D is an estimated k interference-plus-noise level.

44. The method of claim 41 wherein assigning step (c) further comprises selecting a downlink channel that has a minimal computed cost.

45. The method of claim 41 wherein estimating step (a) further comprises:

(i) measuring, at the subscriber station, downlink received signal levels on each downlink channel and reporting the downlink received signal levels to the base station;

(ii) estimating, at the base station, the downlink received interference-plus-noise level from the reported downlink signal levels of measuring step (i).

46. The method of claim 45 wherein measuring step (i) of estimating step (a) further comprises each subscriber station, when not actively engaged in a call, periodically measuring the downlink received signal level on each conventional channel and reporting the downlink received signal levels to the base station.

47. The method of claim 41 wherein the SDMA processing means processes a downlink signal for a particular subscriber station according to a set of downlink multiplexing weights for that particular subscriber station, and wherein step (a) for estimating downlink received interference-plus-noise levels on each downlink channel comprises the following steps:

(i) adjusting, at the base station, each existing subscriber'"'"'s downlink multiplexing weights as if the new subscriber was assigned to a given conventional channel;

(ii) measuring, at the new subscriber station, the downlink received signal level on the given channel after adjusting step (i) and reporting the downlink received signal level to the base station;

(iii) predicting, at the base station, a downlink interference-plus-noise level from the downlink received signal level of measuring step (ii); and

(iv)readjusting, at the base station, each existing subscriber'"'"'s downlink multiplexing weights as if the new subscriber were not assigned to the given conventional channel.

48. The method of claim 41 wherein step (a) for estimating a downlink received interference-plus-noise level, I_k, for each existing channel k comprises, modeling the downlink received interference-plus-noise level, I_k, as a sum of the noise contribution, N_k, and a predicted second interference signal level that would result if the new subscriber was to be assigned to channel k, estimating the noise contribution N_k as a signal level difference between a measured downlink received signal level, P_k, on channel k and a computed first interference signal level due to all base stations using channel k.

49. The method of claim 48 wherein the SDMA Processing means processes a downlink signal for a particular subscriber station according to a set of downlink multiplexing weights for that particular subscriber station, wherein each subscriber station has a downlink spatial signature, and wherein the computed first interference signal level is computed as ##EQU15## where W_k,j^D* =S_k,j^D* =S_k,j A_k,j.sup.†

, S_k,j is a diagonal matrix of base station j transmitted signal amplitudes for conventional channel k, A_k,j is a column-wise concatenated matrix of known spatial signatures at base station j for the subscriber stations on conventional channel k, A_k,j.sup.†

represents the pseudoinverse of A_k,j, and a_k^D,j is a downlink spatial signature for the new subscriber station on conventional channel k from base station j.

50. The method of claim 48 wherein the SDMA processing means processes a downlink signal for a particular subscriber station according to a set of downlink multiplexing weights for that particular subscriber station, wherein each subscriber station has a downlink spatial signature, and wherein the predicted second interference signal level for channel k is computed as ##EQU16## where ##EQU17## †

represents a pseudoinverse operation, S_k,j is a diagonal matrix of transmit signal amplitudes, A_k,j is a column-wise concatenated matrix of known downlink spatial signatures at base station j for the subscriber stations on conventional channel k, a_k^D,j is a downlink spatial signature for the new subscriber station on conventional channel k from base station j, and w^* is the bottom row of matrix S_k,j A_k,j a_k^D,j !.sup.†

.

51. The method of claim 41 further comprising a step for assigning a selected conventional downlink channel only if it is expected to result in an acceptable downlink received signal quality for each active channel based upon at least one downlink quality factor selected from a group consisting of:

cost for new call;

total base station transmitter power;

predicted intermodulation distortion level;

predicted interference-plus-noise level on each active channel; and

predicted signal to interference-plus-noise ratio on each active channel.

52. The method of claim 51 wherein the predicted intermodulation distortion level is obtained by computing a crest factor for each conventional downlink channel, the crest factor value being indicative of an intermodulation distortion level that would result if a given conventional downlink channel were to be assigned.

53. In a wireless communication system, the system including a base station and one or more subscriber stations, the base station including an array of antenna elements and SDMA processing means, a method for assignment of a full-duplex channel in which a duplex channel is selected from a set of duplex channels wherein each duplex channel of the set provides acceptable quality uplink communications, and the downlink channel assignment is made in accordance with existing rules of the system, the method comprising:

(a) computing a cost for each conventional uplink channel according to a cost function that is indicative of a lack of communications quality expected interference level that may be realized by assigning the subscriber station to the conventional uplink channel, the cost function being a function of spatial properties of the subscriber station for communicating with the base station;

(b) assigning a conventional uplink channel by selecting a conventional uplink channel with a cost less than a prescribed cost level; and

(c) selecting a downlink channel in accordance with existing rules of the communication system.

54. The method of claim 53 wherein the full duplex channel assignment is made in accordance with the Personal Handyphone System (PHS) standard.

55. In a wireless communication system, the system including a base station and one or more subscriber stations, the base station including an array of antenna elements and SDMA processing means, the SDMA processing means enabling the base station to communicate on the downlink with more than one subscriber station on the same conventional channel, each subscriber station on the same conventional channel being communicated to by the base station on a different spatial channel of said same conventional channel, a method for assignment of a full-duplex channel in which a duplex channel is selected from a set of duplex channels wherein each duplex channel of the set provides acceptable quality downlink communications, and the uplink channel assignment is made in accordance with existing rules of the system, the method comprising:

(a) computing a cost for each conventional downlink channel according to a cost function that estimates a lack of communications quality expected from existing connections on each conventional downlink channel, if a given conventional downlink channel was assigned;

(b) assigning a conventional downlink channel by selecting a conventional downlink channel with a cost less than a prescribed cost level; and

(c) selecting a uplink channel in accordance with existing rules of the communication system.

56. In a wireless communication system, the system including a base station and one or more subscriber stations, the base station including an array of antenna elements and SDMA processing means, a method for assignment of a full-duplex channel in which a duplex channel is selected from a set of duplex channels wherein each duplex channel of the set provides acceptable quality downlink and uplink communications, the method comprising:

(a) computing a cost for each conventional duplex channel according to a cost function that is indicative of a lack of communications quality expected from existing connections on each conventional duplex channel, the cost function including spatial properties of the subscriber station; and

(b) assigning a conventional duplex channel by selecting a conventional duplex channel with a cost less than a prescribed cost level.

57. A call admission control method, based on an interference cost function, for use in a wireless communication system for controlling admission of a connection for a new subscriber station, the system including a base station and one or more subscriber stations, the base station including an array of antenna elements and SDMA processing means, the method comprising:

(a) evaluating a cost for a selected conventional channel according to a cost function that is indicative of the interference-plus-noise on the selected conventional channel if the selected conventional channel were to be assigned, the evaluation using spatial properties of the subscriber station for communicating with the base station;

(b) comparing the cost with a prescribed channel assignment cost level; and

(c) admitting the call if the cost is less than the prescribed channel assignment cost level.

58. A call admission control method for use in a wireless communication system for controlling admission of a connection for a new subscriber station, the system including a base station and one or more subscriber stations, the base station including an array of antenna elements and SDMA processing means, the method comprising:

(a) predicting the received signal level and interference-plus-noise level on each conventional channel based upon a model of the wireless communication system for predicting a received signal level and interference-plus-noise level on each conventional channel based upon existing connections, if a given conventional channel was assigned for the new subscriber station;

(b) selecting a conventional channel for the new subscriber station that has an acceptably high predicted signal-to-interference-plus-noise ratio (SINR) determined according to predicting step (a); and

(c) admitting the call if the SINR is greater than a prescribed admission level SINR threshold value,

the method further comprising the step of assigning a spatial channel for the call on the selected conventional channel if the communications system supports and the SDMA processing means enables communication on more than one spatial channel on the same conventional channel, and if the assigned conventional channel is in use by the base station for communicating with a second subscriber station on an existing spatial channel.

59. A call admission control method for use in a wireless communication system for controlling admission of a connection of a new subscriber station, the method, based on an estimate of existing system call load, comprising:

(a) estimating the existing call load for indicating how much of the system capacity is being utilized;

(b) prescribing a call load threshold that is indicative of a maximal call load allowed for the system; and

(c) comparing the existing call load with the call load threshold; and

(d) admitting a new call if the estimated existing call load is less than the call load threshold,

wherein estimating step (a) further comprises monitoring the rate at which intracell handoffs occur, and estimating the existing call load from the rate at which intracell handoffs occur.

60. A call admission control method for use in a wireless communication system for controlling admission of a connection of a new subscriber station, the method, based on an estimate of existing system call load, comprising:

(a) estimating the existing call load for indicating how much of the system capacity is being utilized;

(b) prescribing a call load threshold that is indicative of a maximal call load allowed for the system; and

(c) comparing the existing call load with the call load threshold; and

(e) admitting a new call if the estimated existing call load is less than the call load threshold,

wherein estimating step (a) further comprises estimating the existing call load by monitoring the rate of channel reassignments.