Method for exploitation of voice inactivity to increase the capacity of a time division multiple access radio communications system

• US 5,513,183 A
• Filed: 07/27/1994
• Issued: 04/30/1996
• Est. Priority Date: 12/06/1990
• Status: Expired due to Term

• Current Assignee: Hughes Electronics Corporation (Rtx Corporation)
• Original Assignee: Hughes Aircraft Company (Rtx Corporation)
• Inventors: Wendling, Daniel R., Kay, Stanley E., Corrigan, John E. III, Parr, Michael I., Mehta, Ashok D.
• Primary Examiner(s): Olms, Douglas W.
• Assistant Examiner(s): HOM, SHICK C
• Application Number:
  US08/281,389
• Time in Patent Office: 643 Days
• Field of Search: 370/95.1, 370/95.3, 370/85.8, 370/110.1, 370/85.7, 455/33.1, 455/33.2, 455/54.1, 455/54.2, 455/56.1
• US Class Current: 370/337
• CPC Class Codes: G10L 19/012 Comfort noise or silence coding
• CPC Class Codes: H04B 7/26 at least one of which is mobile
• CPC Class Codes: H04B 7/2643 using time-division multiple access [TDMA] H04B7/2615, H04B7/2618 take precedence
• CPC Class Codes: H04J 3/172 Digital speech interpolation, i.e. DSI
• CPC Class Codes: H04W 28/06 Optimizing the usage of the radio link, e.g. header compression, information sizing , discarding information system modifying transmission characteristic according to link quality by modifying frame length H04L1/0007; dynamic adaptation of the packet size for flow control or congestion control H04L47/365
• CPC Class Codes: H04W 72/044 based on the type of the allocated resource
• CPC Class Codes: H04W 72/20 Control channels or signalling for resource management
• CPC Class Codes: H04W 72/21 in the uplink direction of a wireless link, i.e. towards the network
• CPC Class Codes: H04W 72/23 in the downlink direction of a wireless link, i.e. towards a terminal

Abstract

A mobile telephone system multiplexes plural voice traffic channels on a single carrier using a TDMA protocol. The capacity of the mobile telephone system is increased by assigning voice traffic capacity, not on a conversation basis, but on an information burst basis. In order to avoid compromising the voice transmission capacity, control signals (for the allocation and deallocation of both forward and reverse traffic channels) are sent using multiple diversity, i.e. both time and frequency. In addition, to increase the number of available control channels, a control channel comprises a sub-divided portion of an otherwise equivalent voice traffic slot. For reverse allocation requests, which are transmitted over a contention access channel, power diversity is used in addition to time and frequency diversity.

Claims

1. In a radio telephony system having a controlling station and a plurality of controlled stations, the controlling station transmitting and receiving information bursts to and from the controlled stations, the bursts being transmitted on radio carrier frequencies divided into information channels for carrying the information bursts and control channels for carrying control messages controlling the transmission of the information bursts between stations, each channel having a predetermined sequence of carrier frequency time slots, a method for transmitting the information bursts from a selected one of the controlled stations to the controlling station comprising:

upon detection at the controlled station of an information burst, receiving from the controlled station at the controlling station, an information channel allocation request in a first selected control channel slot;

selecting at the controlling station an information channel for transmitting the burst;

transmitting in a second selected control channel slot, from the controlling station to the controlled station, a control message for identifying the selected channel; and

receiving in the selected information channel, from the controlled station at the controlling station, the information burst.

2. The method as recited in claim 1 wherein each control channel is assigned to a different carrier frequency.

3. The method as recited in claim 1 further comprising, before the step of transmitting a control message identifying the selected channel, the step of transmitting a channel allocation request acknowledgment from the controlling station to the controlled station.

4. The method as recited in claim 1 further comprising, after the step of transmitting a control message, the step of transmitting from the controlling station a control message for tuning the controlled station to transmit on only an assigned control channel and the identified information channel.

5. The method as recited in claim 1 further comprising the steps of:

upon detection at the controlled station of the end of the information burst receiving from the controlled station at the controlling station, a channel deallocation request for requesting that the allocation of the selected information channel be withdrawn; and

transmitting, from the controlling station to the controlled station, an acknowledgment for acknowledging withdrawal of the allocation of the selected information channel.

6. The method as recited in claim 5 wherein the step of receiving the deallocation request comprises receiving the deallocation request in the identified information channel as a part of an information burst.

7. The method as recited in claim 1 further comprising, before the step of selecting a first slot, the step of transmitting from the controlling station to the controlled station an identification of each channel within a predetermined set of channels for use in transmitting information between the stations.

8. The method as recited in claim 7 wherein the step of transmitting an identification of each channel further comprises transmitting an abbreviated code for identifying channels in subsequent transmissions and an abbreviated code for identifying the controlled station in subsequent transmissions.

9. The method as recited in claim 7 wherein the step of transmitting an identification of each channel comprises the step of transmitting an identification of the control channel to be used for transmissions by the controlled station.

10. The method as recited in claim 1 wherein the step of transmitting a control message comprises transmitting the control message with frequency, time and power diversity.

11. The method as recited in claim 1 wherein the information burst comprises a speech burst.

12. The method as recited in claim 1 wherein the controlled station comprises a cellular telephone subscriber unit.

13. The method as recited in claim 1 wherein the controlling station comprises a cellular telephony base station and base station controller.

14. In a radio telephony system having a controlling station and a plurality of controlled stations, each controlled station transmitting and receiving information bursts to and from the controlling station, the bursts being transmitted on radio carrier frequencies divided into information channels for carrying the information bursts and control channels for carrying control messages controlling the transmission of the information bursts between stations, each channel having a predetermined sequence of carrier frequency time slots, a method for transmitting the information bursts from a selected one of the controlled stations to the controlling station comprising:

detecting at the controlled station an information burst;

transmitting, from the controlled station to the controlling station, an information channel allocation request in a first selected control channel slot;

receiving in a second control channel slot, from the controlling station at the controlled station, a control message for identifying an information channel for transmitting the burst; and

transmitting in the selected information channel, from the controlled station to the controlling station, the information burst.

15. The method as recited in claim 14 wherein each control channel is assigned to a different carrier frequency.

16. The method as recited in claim 14 further comprising, before the step of receiving a control message identifying the selected channel, the step of receiving a channel allocation request acknowledgment from the controlling station at the controlled station.

17. The method as recited in claim 14 further comprising, after the step of transmitting a control message, the step of tuning the controlled station to transmit on only an assigned control channel and the identified information channel.

18. The method as recited in claim 14 further comprising the steps of:

detecting, at the controlled station, the end of the information burst;

transmitting, from the controlled station to the controlling station, a channel deallocation request for requesting that the allocation of the selected information channel be withdrawn; and

receiving, from the controlling station at the controlled station, an acknowledgment for acknowledging withdrawal of the allocation of the selected information channel.

19. The method as recited in claim 18 Wherein the step of transmitting the deallocation request comprises transmitting the deallocation request in the identified information channel as a part of an information burst.

20. The method as recited in claim 14 further comprising, before the step of selecting a first slot, the step of receiving from the controlling station at the controlled station an identification of each channel within a predetermined set of channels for use in transmitting information between the stations.

21. The method as recited in claim 20 wherein the step of receiving an identification of each channel further comprises receiving an abbreviated code for identifying channels in subsequent transmissions and an abbreviated code for identifying the controlled station in subsequent transmissions.

22. The method as recited in claim 20 wherein the step of receiving an identification of each channel comprises the step of receiving an identification of the control channel to be used for transmissions by the controlled station.

23. The method as recited in claim 14 wherein each control channel slot comprises a plurality of subslots and wherein the step of transmitting an information channel allocation request comprises selecting a control channel subslot for transmitting the request, the controlled station choosing an odd numbered subslot if it has an odd identification number.

24. The method as recited in claim 18 further comprising, after the step of receiving an acknowledgment, the step of tuning the controlled station to receive transmissions from the controlling station only on control channels which have been designated by the controlling station.

25. The method as recited in claim 14 wherein the information burst comprises a speech burst.

26. The method as recited in claim 14 wherein the controlled station comprises a cellular telephone subscriber unit.

27. The method as recited in claim 14 wherein the controlling station comprises a cellular telephony base station and base station controller.

28. A method of implementing TDMA communications between a plurality of user stations, including at least one mobile station, and a base station, said method comprising the steps of:

establishing, at the base station a pool of available traffic transmission channels, each traffic transmission channel comprising a time slot in a repeating time division multiple access frame at a predetermined carrier frequency;

receiving at the base station a request for assignment of a traffic transmission channel, from a mobile station;

in response to receipt of the request at the base station, searching for an available traffic transmission channel from the pool of available traffic transmission channels;

in response to location of an available traffic transmission channel at the base station, transmitting an identification of the located channel to the user station, removing the located channel from the pool of available traffic channels and

receiving an information burst in the located and identified traffic transmission channel of the repeating time division multiple access frame from the user station.

29. A method as recited in claim 28 comprising the further steps of:

receiving from the user station a request for release of the identified traffic transmission channel;

in response to receipt of the request for release at the base station, searching for identification of the traffic transmission channel assigned to the transmitting user station, and

in response to identification of the assigned traffic transmission channel releasing that traffic transmission channel to the pool of available channels.

30. The method as recited in claim 28 further comprising the steps of:

detecting, at the base station, the initiation of an information burst for transmission to a particular user station;

searching for an available traffic transmission channel for transmission from the base station to the particular user station;

in response to locating an available traffic transmission channel transmitting an identification of the located traffic transmission channel to the particular user station and initiating transmission of the information burst to the particular user station using the located traffic transmission channel.

31. The method as recited in claim 30 further comprising the steps of:

detecting, at the base station, termination of the transmitted information burst;

searching for the traffic transmission channel previously assigned for transmission from the base station of the transmitted information burst;

in response to locating the previously assigned traffic transmission channel, transmitting to the particular user station notice of deallocation of the previously assigned traffic transmission channel and releasing the previously assigned channel to the pool.

32. The method as recited in claim 28 wherein the pool also includes control channels each control channel being comprised in a selected time slot in a repeating time division multiple access frame at one of a plurality of different carrier frequencies.