Method of effecting random access in a mobile radio system

• US 5,420,864 A
• Filed: 10/25/1993
• Issued: 05/30/1995
• Est. Priority Date: 10/26/1992
• Status: Expired due to Term

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Muller, Walter, Dahlin, Steinar
• Primary Examiner(s): Olms, Douglas W.
• Assistant Examiner(s): PATEL, AJIT
• Application Number:
  US08/140,467
• Time in Patent Office: 582 Days
• Field of Search: 370/95.1, 370/95.2, 370/95.3, 370/85.2, 370/85.8, 370/85.7, 370/85.6, 340/825.08, 371/204
• US Class Current: 370/347
• CPC Class Codes: H04B 7/2615 using hybrid frequency-time division multiple access [FDMA-TDMA]
• CPC Class Codes: H04W 74/002 Transmission of channel access control information
• CPC Class Codes: H04W 74/006 in the downlink, i.e. towards the terminal
• CPC Class Codes: H04W 74/0833 Random access procedures, e.g. with 4-step access
• CPC Class Codes: H04W 74/0875 with assigned priorities based access

Abstract

A method for random access in a time divided mobile radio system, for instance an FDMA/TDMA system, which includes digital traffic channels and control channels which are organized so that four traffic channels and two control channels are included in a TDMA-frame. A base station transmits continually flags in the time slots of the control channels. A mobile station desiring access to the system responds by sending a first message word (W1) in the time slot indicated by the base station in a first flag. When the mobile station wishes to transmit several message words, the base station reserves one or more time slots to this end by transmitting the first flag, although this flag now states that these time slots are busy for other mobile stations. Furthermore, the base station transmits a flag (R/N) which states whether or not a message word has been received from the mobile station. The base station can transmit a further flag, which denotes that a given time slot has been reserved for a given mobile station from the very beginning of an access procedure and cannot therefore be used by any other mobile station.

Claims

1. A random access method in a time division multiple access mobile radio system, in which control channels and traffic channels are formed by time slots within a frame, and which includes a primary station and a plurality of secondary stations, each of which sends access messages in the form of short message words during time slots allocated by the primary station, comprising the steps of:

sending from the primary station first flags, each first flag being associated with a respective time slot and denoting a state whether or not the respective associated time slot during which a secondary station shall transmit a message word to the primary station is idle or busy,

initiating a communication by sending, from one of the secondary stations in response to a received first flag denoting an idle state, a first one of the message words in the time slot associated with the received first flag and sending, from the one of the secondary stations, subsequent ones of the message words in subsequent time slots associated with first flags that indicate to other secondary stations that the subsequent time slots are busy,

sending from the primary station together with the first flags, second flags, each second flag indicating to the sending secondary station whether or not the primary station has received a respective one of the message words sent by the sending secondary station, and

requesting retransmission of only one message word in an access message that has not been correctly received.

2. The method of claim 1, wherein after having received the first message word, the primary station again transmits a first flag which denotes that the associated time slot is allocated to the sending secondary station if the sending secondary station intends to transmit more message words, and together with the first flag transmits the second flag which acknowledges whether or not the first message word has been received by the primary station.

3. The method of claim 2, wherein when the primary station has not received the first message word, the second flag includes a request for the first message word to be retransmitted by the sending secondary station in the time slot allocated by the primary station according to the first flag.

4. A method according to claim 1, wherein the primary station, in addition to the first and second flags, transmits together with said flags, third flags to all secondary stations, each third flag indicating that an associated predetermined time slot is reserved for a predetermined secondary station for the purpose of sending a first one of the message words from the predetermined secondary station.

5. A method of detecting a flag in conjunction with random access in a time division multiple access mobile radio system, in which control channels and traffic channels are formed by time slots within a frame and which comprises a primary station and a plurality of secondary stations, each of which transmits access messages in the form of short message words during time slots allocated by the primary station, including the steps of:

continually transmitting flags, each flag indicating a state whether an associated time slot, during which a secondary station shall transmit a message word to the primary station, is idle or busy, and

transmitting from one of the secondary stations in response to a received flag transmitted by the primary station, a first one of the message words in the associated time slot indicated by the received flag as idle and transmitting succeeding ones of the message words in succeeding time slots that are indicated to other secondary stations as busy by the associated flags, and

wherein each flag has one of a first plurality of binary values to indicate a first state of the associated time slot and one of a second plurality of binary values to indicate a second state of the associated time slot, and the first plurality of binary values is greater than the second plurality of binary values when the first state shall be given priority over the second state.

6. The method of claim 5, wherein said priority is given by the transmitting secondary station after the transmitting secondary station has transmitted the first one of the message words and has received a succeeding flag when the transmitting secondary station intends to send a further message word.

7. A method of detecting a flag in conjunction with random access in a time division multiple access mobile radio system, in which control channels and traffic channels are formed by time slots within a frame, and which includes a primary station and a plurality of secondary stations of which each transmits access messages in the form of short message words, each within a time slot which is allocated by the primary station, including the steps of:

transmitting a succession of flags, wherein each flag has one of two states denoting whether an associated time slot, during which a secondary station shall transmit a message word to the primary station, has earlier been reserved or is free,

transmitting, from one of the secondary stations in response to a flag transmitted from the primary station, the message word in the associated time slot that the primary station has indicated as reserved, and

detecting the transmitted flag in the secondary station, and evaluating a binary value of the transmitted flag,

wherein the transmitted flag has one of a plurality of binary values to indicate one state of the flag and a second plurality of binary values to indicate another state of the flag, and the number of the first plurality of binary values is greater than the number of the second plurality of binary values when the one state of the flag shall be given priority over the other state of the flag.