Radio communication apparatus and packet scheduling method

• US 7,359,735 B2
• Filed: 02/04/2005
• Issued: 04/15/2008
• Est. Priority Date: 03/03/2004
• Status: Expired due to Fees

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi Advanced Systems Corp. (Hitachi, Ltd.), Hitachi Communication Technologies, Ltd. (Hitachi, Ltd.), Hitachi, Ltd.
• Inventors: Kuwahara, Mikio, Fujishima, Kenzaburo, Okamoto, Toru, Taira, Masanori, Meguro, Koji
• Primary Examiner(s): Perez-Gutierrez; Rafael
• Assistant Examiner(s): GONZALEZ, AMANCIO
• Application Number:
  US11/049,752
• Publication Number:
  US 20050197162A1
• Time in Patent Office: 1,166 Days
• Field of Search: 370/241, 370/395, 370/347, 370/444, 455/63.4, 455/69, 455/561, 455/562.1
• US Class Current: 455/562.1
• CPC Class Codes: H04B 7/0408 using two or more beams, i.e. beam diversity
• CPC Class Codes: H04W 16/28 using beam steering
• 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

Abstract

A radio communication apparatus enhances cell throughput by adaptive selection of spatially multiplexed channels in consideration of interferences in a local cell and reducing load for calculation of array weights by storing them in advance as fixed values and outputting fixed beams. To reduce the calculation load for the adaptive selection of spatially multiplexed channels that takes interferences within the local cell into consideration, the radio communication apparatus adopts a packet scheduling method that selects a combination of fixed beams and determines the number of spatially multiplexed channels, based on the fixed beams for mobile apparatuses with packets waiting to be transmitted and pre-calculated correlative quantities of inter-beam interferences between these fixed beams.

Claims

1. A packet scheduling method in a radio communication apparatus having array antennas and transmitting packets to a plurality of mobile apparatuses using a plurality of fixed beams created by the array antennas, the method comprising:

a first step of selecting one of the fixed beams for communication with each of said mobile apparatuses residing in the coverage of the radio communication apparatus, and associating the selected fixed beam with the mobile apparatus;

a second step of estimating respective states of radio channels toward the mobile apparatuses;

a third step of selecting a specific combination of fixed beams to be output, based on expectation values of inter-beam interference quantities each estimated in advance and stored, in a management table formed in a memory, in association with each of combinations of beam identifiers indicating a plurality of simultaneously transmittable fixed beams, associations between the mobile apparatuses and the fixed beams associated in said first step, and the states of radio channels estimated in said second step; and

a fourth step of generating by said array antennas, the fixed beams in said specific combination selected in said third step, and transmitting packets to the mobile apparatuses corresponding to the fixed beams in the selected combination,

wherein said specific combination of fixed beams is selected in said third step according to the state of radio channels toward mobile apparatuses associated with the fixed beams, from among a plurality of available combinations of fixed beams having been determined based on said management table to have inter-beam interference quantity less than a predetermined threshold.

2. The packet scheduling method according to claim 1, wherein said third step evaluates transmission rates for each of said mobile apparatuses or each of said fixed beams based on the states of said radio channels and preferentially selects as said specific combination, a combination of fixed beams including a fixed beam corresponding to a mobile apparatus having a high transmission rate or a fixed beam having a high transmission rate.

3. The packet scheduling method according to claim 1, wherein said third step preferentially selects as said specific combination, a combination of fixed beams including a fixed beam of low transmission performance or a fixed beam corresponding to a mobile apparatus for which the transmission performance is low, by referring to past transmission records for each of said fixed beams or for each of said mobile apparatuses associated with each fixed beam.

4. The packet scheduling method according to claim 1, wherein said third step preferentially selects as said specific combination, a combination of fixed beams including a fixed beam corresponding to a mobile apparatus for which the amount of packets waiting to be transmitted is large or a fixed beam for which the amount of packets waiting to be transmitted is large, by referring to the amount of packets waiting to be transmitted to each mobile apparatus.

5. The packet scheduling method according to claim 1, wherein said first step estimates an angle of arrival of signals received from each of said mobile apparatuses and associates the mobile apparatus with a fixed beam for transmitting a signal in the direction corresponding to the estimated angle of arrival.

6. The packet scheduling method according to claim 1, wherein said first step associates an ID of a fixed beam notified from each of said mobile apparatuses as an optimal beam for the mobile apparatus with the ID of the mobile apparatus.

7. A radio communication apparatus for transmitting packets to a plurality of mobile apparatuses using a plurality of fixed beams created by array antennas, said radio communication apparatus comprising:

a storage including a first management table for storing a plurality of combination of array weights by which the plurality of fixed beams are created and a second management table for storing expectation values of inter-beam interference quantities estimated in advance for each of combinations of beam identifiers indicating a plurality of simultaneously transmittable fixed beams;

a processor for packet scheduling;

a beam former for creating the beams to transmit the packets according to the array weights designated from the processor; and

array antennas for transmitting the packets, using the fixed beams created by the beam former,

wherein said processor performs;

allocating one of said fixed beams to each of said plurality of mobile apparatuses;

associating an identifier of each of said mobile apparatuses with one of identifiers of said fixed beams and storing the associations into a third management table formed in said storage;

obtaining respective states of radio channels toward the plurality of mobile apparatuses;

selecting a specific combination of fixed beams to be output, based on inter-beam interference quantities for each combination of simultaneously transmittable fixed beams indicated by said first management table, the associations between the mobile apparatus identifiers and fixed beam identifiers stored in said third management table, and the states of the radio channels;

generating transmission packets to be transmitted to mobile apparatuses associated with the fixed beams in the specific combination;

retrieving array weights corresponding to the fixed beams in the specific combination from said second management table; and

outputting the array weights and the transmission packets to said beam former,

wherein said specific combination of fixed beams is selected, according to the state of radio channels toward mobile apparatuses associated with the fixed beams, from among a plurality of available combinations of fixed beams having been determined based on said second management table to have inter-beam interference quantity less than a predetermined threshold.

8. The radio communication apparatus according to claim 7, wherein said processor estimates the angle of arrival of signals transmitted from each of said mobile apparatuses and received by said array antennas and allocates a fixed beam in the direction corresponding to the estimated angle to each of said mobile apparatuses.

9. The radio communication apparatus according to claim 7, wherein said processor associates the ID of a fixed beam, which has been notified from a mobile apparatus as an optimal beam for the mobile apparatus, with the ID of the mobile apparatus.

10. The radio communication apparatus according to claim 7, wherein said processor evaluates transmission rates for each of said mobile apparatus or for each of said fixed beams based on the states of said radio channels, and preferentially selects as said specific combination, a combination of fixed beams including a fixed beam corresponding to a mobile apparatus at a high transmission rate or a fixed beam having a high transmission rate.

11. The radio communication apparatus according to claim 7, wherein said processor evaluates past transmission performance for each of said fixed beams or for each of said mobile apparatuses associated with one of said fixed beams, and preferentially selects as said specific combination, a combination of fixed beams including a fixed beam for which the past transmission performance is low or a fixed beam corresponding to a mobile apparatus for which the past transmission performance is low.

12. The radio communication apparatus according to claim 7, wherein said processor preferentially selects as said specific combination, a combination of fixed beams including a fixed beam corresponding to a mobile apparatus for which the amount of packets waiting to be transmitted thereto is large or a fixed beam for which the amount of packets waiting to be transmitted thereon is large.