Fixed frequency-time division duplex in radio communications systems

• US 6,587,444 B1
• Filed: 11/12/1998
• Issued: 07/01/2003
• Est. Priority Date: 11/14/1997
• Status: Expired due to Fees

• Current Assignee: Ericsson, Inc. (Telefonaktiebolaget LM Ericsson)
• Original Assignee: Ericsson, Inc. (Telefonaktiebolaget LM Ericsson)
• Inventors: Lenzo, Michael, Shen, Qun
• Primary Examiner(s): Kizou, Hassan
• Assistant Examiner(s): Tsegaye, Saba
• Application Number:
  US09/189,807
• Time in Patent Office: 1,692 Days
• Field of Search: 370/328, 370/330, 370/336, 370/337, 370/344, 370/345, 370/347, 370/377, 370/276-277, 370/280, 370/281, 370/294, 370/295, 370/436, 370/478, 445/447, 445/450, 445/62
• US Class Current: 370/330
• CPC Class Codes: H04B 7/2615 using hybrid frequency-time division multiple access [FDMA-TDMA]

Abstract

A flexible channel architecture supports full-duplex, radio-frequency communication between a base station, such as a PWT or DECT base station, and a group of remote terminals. Communication from the base to the terminals is by way of a radio-frequency carrier having a first frequency, and communication from the terminals to the base is by way of a second radio-frequency carrier having a second frequency. Each carrier is organized to provide an N-timeslot time-division multiple access data stream (N an integer), so that together the two carriers provide a 2N-timeslot system. Within each data frame, data from the base to the terminals is sent on the first carrier during a first half of the frame, and data from the terminals to the base is sent on the second carrier during the remaining half of the frame. An additional, complimentary base station, constructed to transmit when the first base station is receiving and vice versa, can be co-located with the first base station to provide full time and spectral efficiency within a coverage area serviced by the base stations.

Claims

1. A base station for use in a wireless communications system including a plurality of mobile stations, said base station comprising:

a transceiver configured to transmit downlink communications signals to said mobile stations via a first carrier frequency and to receive uplink communications signals from said mobile stations via a second carrier frequency, the downlink and uplink communications signals being transmitted and received via successive time division multiple access frames, each frame including a plurality of time slots in each of the first carrier frequency and the second carrier frequency,

wherein, for each active communications link between said base station and a particular mobile station, a first time slot in each frame is allocated for downlink communication to the particular mobile station and a second time slot in each frame is allocated for uplink communication from the particular mobile station, the first and second allocated time slots being separated in time by a fixed time offset, and

wherein a first partition of the time slots within each frame is reserved for downlink communications from said base station to the mobile stations and a second partition of the time slots within each frame is reserved for uplink communications from the mobile stations to said base station, such that a first portion of the time slots within each frame are reserved for downlink communications and a second portion of the time slots within each frame are reserved for uplink communications.

2. A base station according to claim 1, wherein a duration of the fixed time offset is the same for each active communications link.

3. A base station according to claim 2, wherein each frame is of a duration T and includes a number, 2N, of time slots, each time slot being of a duration T/2N, and wherein the duration of the fixed time offset for each active communications link is T/2.

4. A base station according to claim 1, wherein a downlink signal processing path and an uplink signal processing path of said transceiver share common signal processing components.

5. A base station according to claim 4, wherein said shared signal processing components include at least one of a filter, a local oscillator and a modem.

6. A wireless communications system, comprising:

a plurality of mobile stations; and

a first base station configured to transmit downlink communications signals to said mobile stations via a first carrier frequency and to receive uplink communications signals from said mobile stations via a second carrier frequency, the downlink and uplink communications signals being transmitted and received via successive time division multiple access frames, each frame including a plurality of time slots in each of the first carrier frequency and the second carrier frequency,

wherein, for each active communications link between said first base station and a mobile station, a first time slot in each frame is allocated for downlink communications and a second time slot in each frame is allocated for uplink communications, the first and second allocated time slots being separated in time by a fixed time offset, and

wherein a first partition of the time slots within each frame is reserved for downlink communications from said first base station to the mobile stations and a second partition of the time slots within each frame is reserved for uplink communications from the mobile stations to said first base station, such that a first portion of the time slots within each frame are reserved for downlink communications and a second portion of the time slots within each frame are reserved for uplink communications.

7. A communications system according to claim 6, wherein a duration of the fixed time offset is the same for each active communications link.

8. A communications system according to claim 7, wherein each frame is of a duration T and includes a number, 2N, of time slots, each time slot being of a duration T/2N, and wherein the duration of the fixed time offset for each active communications link is T/2.

9. A communications system according to claim 6, wherein a downlink signal processing path and an uplink signal processing path of said first base station share common signal processing components.

10. A communications system according to claim 9, wherein said shared signal processing components include at least one of a filter, a local oscillator and a modem.

11. A method for conducting communications between base stations and mobile stations in a wireless communications system, comprising the steps of:

co-locating at least two base stations;

transmitting communications signals between the co-located base stations and the mobile stations using time division multiple access frames, each frame including a plurality of time slots, wherein downlink communications signals from the co-located base stations to the mobile stations are transmitted via a first carrier frequency and uplink communications signals from the mobile stations to the co-located base stations are transmitted via a second carrier frequency; and

for each of the co-located base stations, reserving first and second partitions of time slots within each frame for downlink and uplink communications, respectively, such that, at any moment in time, at most one of the co-located base stations is transmitting via the first carrier frequency and at most one of the co-located base stations is receiving via the second carrier frequency.

12. A wireless communications system, comprising:

a plurality of mobile stations; and

a first base station configured to transmit downlink communications signals to said mobile stations via a first carrier frequency and to receive uplink communications signals from said mobile stations via a second carrier frequency, the downlink and uplink communications signals being transmitted and received via successive time division multiple access frames, each frame including a plurality of time slots,

wherein, for each active communications link between said first base station and a mobile station, a first time slot within each frame is allocated for downlink communications and a second time slot within each frame is allocated for uplink communications, the first and second allocated time slots being separated in time by a fixed time offset, and

wherein a first partition of the time slots within each frame is reserved for downlink communications from said first base station to the mobile stations and a second partition of the time slots within each frame is reserved for uplink communications from the mobile stations to said first base station;

at least one additional base station co-located with said first base station and configured to transmit downlink communications signals to said mobile stations via the first carrier frequency and to receive uplink communications signals from said mobile stations via the second carrier frequency, the downlink and uplink communications signals of each of said additional base stations being transmitted and received via successive time division multiple access frames, each frame including a plurality of time slots,

wherein, for each active communications link between an additional base station and a mobile station, a first time slot within each frame of said additional base station is allocated for downlink communications from said additional base station and a second time slot within each frame of said additional base station is allocated for uplink communications to said additional base station, the first and second allocated time slots being separated in time by a fixed time offset,

wherein a first partition of the time slots within each frame of each additional base station is reserved for uplink communications and a second partition of the time slots within each frame of each additional base station is reserved for downlink communications, and

wherein the first and second partitions of the frames of each of said base stations are structured such that, for each time slot in each frame, only one of said base stations is permitted to transmit on the first carrier frequency and only one of said base stations is permitted to receive on the second carrier frequency.

13. A communications system according to claim 12, wherein a first half of the time slots within each frame are reserved for downlink communications and a second half of the time slots within each frame are reserved for uplink communications.

14. A communications system according to claim 12, wherein, for N a positive integer and M a positive integer less than or equal to 2N, 2N being equally divisible by M, each frame includes 2N time slots, a first 2N/M of which time slots are reserved for downlink communications and a second 2N/M of which time slots are reserved for uplink communications.

15. A communications system according to claim 12, wherein a duration of the fixed time offset is the same for each active communications link.

16. A communications system according to claim 15, wherein each frame is of a duration T and includes a number, 2N, of time slots, each time slot being of a duration T/2N, and wherein the duration of the fixed time offset for each active communications link is T/2.

17. A communications system according to claim 12, wherein a downlink signal processing path and an uplink signal processing path of said first base station share common signal processing components.

18. A communications system according to claim 17, wherein said shared signal processing components include at least one of a filter, a local oscillator and a modem.

19. A communications system according to claim 12, wherein said first base station is co-located with a single additional base station,

wherein first and second halves of the time slots of each frame of said first base station coincide in time with first and second halves, respectively, of each frame of said single additional base station,

wherein the first and second halves of the time slots of each frame of said first base station are reserved, respectively, for downlink communications from said first base station and uplink communications to said base station, and

wherein the first and second halves of the time slots of each frame of said single additional base station are reserved, respectively, for uplink communications to said single additional base station and downlink communications from said single additional base station.