MULTI-BEAM CELLULAR COMMUNICATION SYSTEM

• US 20140226517A1
• Filed: 04/21/2014
• Published: 08/14/2014
• Est. Priority Date: 03/11/2003
• Status: Active Grant

• Current Assignee: Blackberry Limited
• Original Assignee: Blackberry Limited
• Inventors: Wilson, Fiona, Gale, Simon
• Granted Patent: US 9,125,202 B2
• Time in Patent Office: Days
• US Class Current: 370/252
• CPC Class Codes: H01Q 1/246 specially adapted for base stations
• CPC Class Codes: H01Q 21/205 providing an omnidirectional coverage turnstile aerials H01Q21/26
• CPC Class Codes: H01Q 25/002 providing at least two patterns of different beamwidth; Variable beamwidth antennas
• CPC Class Codes: H01Q 3/2617 Array of identical elements
• 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 7/2628 using code-division multiple access [CDMA] or spread spectrum multiple access [SSMA] H04B7/2618 takes precedence
• CPC Class Codes: H04J 13/0044 OVSF [orthogonal variable spreading factor]
• CPC Class Codes: H04J 13/0048 Walsh
• CPC Class Codes: H04L 1/0003 by switching between different modulation schemes
• CPC Class Codes: H04L 1/0009 by adapting the channel coding H04L1/1812 takes precedence
• CPC Class Codes: H04L 5/0007 the frequencies being orthogonal, e.g. OFDM(A), DMT
• CPC Class Codes: H04L 5/005 of common pilots, i.e. pilots destined for multiple users or terminals
• CPC Class Codes: H04W 16/24 Cell structures
• CPC Class Codes: H04W 16/28 using beam steering
• CPC Class Codes: H04W 24/08 Testing, supervising or monitoring using real traffic
• CPC Class Codes: H04W 52/42 in systems with time, space, frequency or polarisation diversity
• CPC Class Codes: H04W 72/0446 Resources in time domain, e.g. slots or frames

Abstract

A cellular communication system comprising a plurality of geographically spaced base stations (2) each of which comprises an antenna arrangement (4, 6, 8) per base station sector, each of which antenna arrangements has an antenna element for generating an array of narrow beams (10, 12, 14) covering the sector. Timeslots are simultaneously transmitted over each of the beams so as to generate successive sets of simultaneously transmitted timeslots per sector. The timeslots are each split into multiple orthogonal codes, for example Walsh codes. The communication system additionally comprising a scheduling device (31) for allocating for successive sets of timeslots common overhead channels, including a common pilot channel, which are allocated to the same sub-set of codes of each timeslot in the set. For successive sets of timeslots different data traffic is allocated to the same sub-set of codes of each timeslot in the set. This effectively generates a sector wide antenna beam carrying the common overhead channels and a plurality of narrow beams each of which carry different data traffic. Inter-beam interference is addressed by the application of Adaptive Modulation and Coding and by an inter-beam handoff scheme. The handoff scheme ensures that when an end user equipment is located in a cusp region between adjacent beams the antenna arrangement simultaneously transmits data traffic to that mobile station on at least both of the adjacent beams.

Claims

1. A method for use in a cellular communication system comprising at least one base station (2) the or each of which comprises an antenna arrangement (4,6, 8) per base station sector for generating an array of narrow beams (10. 12. 14) covering the sector, which method comprising the steps of:

simultaneously transmitting timeslots over each beam;

generating multiple codes in each time slot;

transmitting common overhead channels including a pilot channel to end user equipments on each beam in a sector using the same sub-set of codes; and

transmitting different data traffic to end user equipments on different beams in a sector by re-using the same codes in each beam.

2. A method according to claim 1 wherein the steps of:

simultaneously transmitting timeslots over each beam generates successive sets of simultaneously transmitted timeslots;

transmitting the common overhead channels comprises the step of allocating the same sub-set of codes in each timeslot of a set of timeslots to the common overhead channels; and

transmitting different data traffic comprises the step of allocating a sub-set of codes in each timeslot of a set of timeslots to different data traffic.

3. A method according to claim 1 wherein the multiple codes are multiple orthogonal codes.

4. A method according to claim 1 comprising the steps of:

determining when an end user equipment (1) is located in a cusp region between two adjacent beams; and

in response to such a determination sending data traffic for that end user equipment on the same codes simultaneously in at least the two adjacent beams.

5. A method according to claim 1, comprising the steps of:

measuring the carrier/interference levels on the pilot channel; and

in response to the measured level applying appropriate modulation and coding to the signals transmitted on the beams.

6. A method according to claim 1, comprising the steps of:

transmitting a unique auxiliary pilot signal on each beam;

measuring the carrier/interference levels on the auxiliary pilot signals of all beams within the sector;

calculating the carrier/interference level for the beam received at the highest power by subtracting the carrier power of all other auxiliary pilots from the carrier level of the highest power beam; and

in response to the calculated level applying appropriate modulation and coding to the signals transmitted on the highest power beam.

7. A method according to claim 1 wherein sub-sets of codes allocated to different data traffic include a different number of codes in simultaneously transmitted timeslots associated with adjacent beams.

8. A cellular communication system comprising at least one base station (2) the or each of which comprises an antenna arrangement (4, 6, 8) per base station sector, each of which antenna arrangements having a beamforming device for generating an array of narrow beams (10,12,14) covering the sector, over each of which beams timeslots are simultaneously transmitted which timeslots are each split into multiple codes, wherein the or each base station is arranged to transmit common overhead channels including a pilot channel to end user equipments in each beam in a sector using the same sub-set of codes and to transmit different data traffic to end user equipments on different beams in a sector by re-using the same codes in each beam.

9. A communication system according to claim 8 wherein the antenna arrangement transmits successive sets of simultaneously transmitted timeslots per sector and the communication system additionally includes a base station controller (31) for allocating the common overhead channels to the same sub-set of code of each timeslot in a set of timeslots and for allocating different data traffic to a sub-set of codes of each times/at in a set of timeslots.

10. A communication system according to claim 8 wherein the multiple codes are multiple orthogonal codes.

11. A communication system according to claim 8 in which each base station comprises processing means for determining when an end user equipment (1) is located in a cusp region between two adjacent beams, and in response to such a determination the processing means is arranged to send data traffic for that end user equipment simultaneously on at least the two adjacent beams.

12. A communication system according to claim 8 in which a base station additionally comprises processing means for determining the carrier/interference levels on the pilot channel and in response to the measured level applying appropriate modulation and coding to the signals transmitted on the beams.

13. A communication system according to claim 8 in which the antenna arrangement transmits a unique auxiliary pilot signal on each beam and the base station additionally comprises means for measuring the carrier/interference levels on the auxiliary pilot channel of all beams within the sector;

means for calculating the carrier/interference level for the beam received at the highest power by subtracting the carrier power of all other auxiliary pilots from the carrier level of the highest power beam and means for, in response to the calculated level, applying appropriate modulation and coding to the signals transmitted on the highest power beam.

14. A communication system according to claim 8 wherein sub-sets of codes allocated to different data traffic include a different number of codes in simultaneously transmitted timeslots associated with adjacent beams.

15. Computer readable media for installation on a base station controlling device of a cellular communication system for controlling a base station (2) which comprises an antenna arrangement (4,6, 8) per base station sector for generating an array of narrow beams (10,12,14) covering the sector, in which each antenna arrangement simultaneously transmits timeslots over each beam to generate successive sets of simultaneously transmitted timeslots and in which each time slot is split into multiple codes;

which computer readable media carries out the steps of

allocating the same sub-set of codes in each timeslot of a set of timeslots to common overhead channels including a pilot channel; and

allocating a sub-set of codes in each timeslot of a set of timeslots to different data traffic so as to transmit different data traffic on different beams by re-using the same codes in each beam.

16. Computer readable media according to claim 15 wherein the multiple codes are multiple orthogonal codes.

17. Computer readable media according to claim 15 for carrying out the steps of the steps of:

determining when an end user equipment (1) is located in a cusp region between two adjacent beams; and

in response to such a determination sending data traffic for that end user equipment on the same sub-set of codes in the timeslots of a set of timeslots associated with at least the two adjacent beams.

18. Computer readable media according to claim 15 for carrying out the steps of:

measuring the carrier interference levels on the pilot channel; and

in response to the measured level applying appropriate modulation and coding to the signals transmitted on the beams.

19. Computer readable material according to claim 15 for installation on a base station controlling device of a communication system in which a unique auxiliary pilot signal is transmitted on each beam, for carrying out the steps at measuring the carrier interference levels on the auxiliary pilot channels of all beams in a sector;

and

calculating the carrier/interference level for the beam received at the highest power by subtracting the carrier power of all other auxiliary pilots in the sector from the carrier level of the highest power beam; and

in response to the calculated level applying appropriate modulation and coding to the signals transmitted on the highest power beam.

20. Computer readable media according to claim 15 wherein the step of allocating the same sub-set of codes in each timeslot of a set of timeslots to different data traffic includes the step of making the sub-sets associated with adjacent beams include a different number of codes.

21-44. -44. (canceled)