Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W72/00—Local resource management
  • H04W72/50—Allocation or scheduling criteria for wireless resources
  • H04W72/56—Allocation or scheduling criteria for wireless resources based on priority criteria
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W72/00—Local resource management
  • H04W72/12—Wireless traffic scheduling

Definitions

• This invention relates to digital data and control message transmission in predetermined
• the present invention relates to a method of transmitting control messages in predetermined time slots within fixed length time frames from a first transmitting and receiving unit to a second transmitting and receiving unit for controlling the second unit, the control message comprising data of the availability of carrier radio frequencies to the second unit for communication with first unit.
• the availability data indicates which carrier radio frequencies are preferred for use, which are less preferred for use, and which are not for use. It is preferred that the availability data is updated
• the invention also relates to a corresponding method of transmitting digital data signals, a transmitter, and communication means.
• Figure 1 is a schematic diagram illustrating the system including a base station (BTE - Base Terminating Equipment) and subscriber unit (NTE - Network Terminating
• Figure 2 is a diagram illustrating frame structure and timing for a duplex link
• Figure 3 is a diagram representing a slot-list message from a base station.
• the preferred system is part of a telephone system in which the
• the preferred system includes the duplex radio link, and transmitters and receivers for implementing the necessary protocol.
• the preferred system includes the duplex radio link, and transmitters and receivers for implementing the necessary protocol.
• GSM digital cellular mobile telephone systems
• GSM Global System for Mobile communications
• PHY Physical
• MAC Medium Access Control
• DLC Data Link Control
• NWK Network
• directional antennae and mains electricity can be used.
• Each base station in the preferred system provides six duplex radio links at twelve frequencies chosen from the overall frequency allocation, so as to minimise interference between base stations nearby.
• the frame structure and timing for the duplex link is illustrated in Figure 2.
• Each duplex radio link comprises an up-link from a subscriber unit to a base station and, at a fixed frequency offset, a down-link from the base station to the subscriber unit.
• the down-links are TDM, and the up-links are TDMA.
• Modulation for all links is n/4 - DQPSK, and the basic frame structure for all links is ten slots per frame of 2560 bits, i.e. 256 bits per slot.
• the bit rate is 512kbps.
• Down ⁇ links are continuously transmitted and incorporate a b- ⁇ dcast channel for essential system information. When there is no useful information to be transmitted, the downlink transmission continues to use the basic frame and slot structure and contain a suitable fill pattern and essential broadcast channel.
• normal slots which are used after call set-up
• pilot slots which are used during call set-up
• Each down-link normal slot comprises 24 bits of synchronisation information followed by 24 bits designated S-field which includes an 8 bit header, followed by 160 bits designated D-field. This is followed by 24 bits of Forward Error Correction, and an 8 bit tail, followed by 12 bits of broadcast channel.
• the broadcast channel consists of segments in each of the slots within a frame which together form the down-link common signalling channel which is transmitted by the base station, and contains control messages containing link information such as slot lists, multi-frame and super-frame information and other information, connectionless messages and information basic to the operation of the system.
• each down-link slot contains frequency correction data and/or a training sequence for receiver initialisation with only a short S- field and no D- field
• Up-link slots basically contain two different types of data packet.
• pilot packet is used before a connection is set up, for example, for an
• ALOHA call request and to allow adaptive time alignment.
• the other type of data is
• a normal packet is used when a call has been established and is a larger data packet, due to the use of adaptive time alignment.
• Each up-link normal packet contains a data packet of 244 bits which is preceded and followed by a ramp of 4 bits duration.
• the ramps and the remaining bits left of the 256 bit slot provide a guard gap against interference from neighbouring slots due to timing
• Each subscriber unit adjusts the timing of its slot transmissions to compensate for the time it takes signals to reach the base station.
• Each up-link pilot slot contains a pilot data packet which is 92 bits long preceded and followed by 4 bit ramp defining an extended guard gap of 60 bits. This larger guard gap is necessary because there is no timing information available, and without it,
• the pilot packet comprises 64 bits of sync followed by 104 bits of S-field which starts with an 8 bit header and finishes with a 16 bit Cyclic Redundancy Check 2 reserved bits, 14 forward error correction FEC bits, and 8 tail bits. There is no D-field.
• the S-fields in the above mentioned data packets can be used for two types of signalling.
• the first type is MAC signalling (MS) and is used for signalling between the MAC layer of the base station and the MAC layer of a subscriber unit in which timing is important.
• the second type is called associated signalling, which can be slow or fast, and is used for signalling between the base station and the subscriber units in the DLC or NWK layers.
• General encryption is provided by combining the speech or data with a non-predictable sequence of cipher bits produced by a key stream generator which is synchronised to the transmitted super-frame number.
• the transmitted signal is scrambled to remove dc components.
• a slotted Aloha protocol is used by subscriber units to send call set-up requests and short information messages (Datagrams) to the base station. These requests and messages are sent in a pilot packet in one of a list of slots, known as Aloha slots, that have been designated as available for this purpose in a Slot-List broadcast by the base station.
• a typical slot-list broadcast is illustrated in Figure 3.
• a slot-list is valid for a multiframe, which consists of sixteen consecutive frames numbered 0 - 15, and is broadcast in one multiframe to be applicable to the following multiframe. The number
• Each slot-list message may designate up to three Aloha slots, as shown in the Figure 3.
• a minimum number of slot-list messages are used, and these are each assigned a sequence number and are sent in ascending order, and are re-transmitted in the same order following complete transmission within the same multiframe. Typically, however, a single slot-list message will be sufficient to transmit the complete Slot-List.
• the broadcast channel itself comprises a predetermined portion of each slot in every frame of the multiframe, and is used to broadcast various messages besides slot-list messages. Furthermore, different priorities are allocated to these different types of messages. Thus in frames 0 to 7 of a multiframe, slot-list messages have the lowest priority, and may not be transmitted because of the volume of other messages. However, slot-list messages are given a high priority in frames 8, 9, 12 and 13 so that transmission of at least a part, and most probably all, of the Slot-List is guaranteed.
• the information in the Slot-List is encoded for reduced bandwidth, and has to be decided by reference to a Carrier-List which includes details of bearer frequencies.
• This Carrier-List is also transmitted in the broadcast channel in frame 15 of the multiframe preceding that in which the Slot-List is transmitted.
• the base station sends information specific to each subscriber unit of which RF carrier
• Each subscriber unit stores this information.
• RF frequencies are categorised as 'black' if, for example, their use by one sector is
• the base station controls which slots are to be included in the Slot-List taking into
• the Aloha slots can be
• An Access Control Indicator is incorporated in each slot-list message and is the same for all segments of a segmented slot-list message.
• the Access Control Indicator is used
• the Access Control Indicator may take an integer value between 1 and 4.
• the services may take an integer value between 1 and 4.
• Each subscriber unit maintains a Classified Carrier-List corresponding to the information
• a subscriber unit receives Aloha slot-list messages on the broadcast channel, starting with the first slot-list message in a multi frame, and compiles a valid Slot-List for the
• Classified Carrier-List or which are not of the appropriate type (call set-up requests or
• RF frequencies categorised 'white' are preferred to those categorised 'grey'.
• the subscriber unit Following reception of the final slot-list message in a sequence, the subscriber unit
• a message which is either a datagram or a
• the datagram or call set-up request is sent to the base station in the selected slot at the next possible opportunity according to the setting of an extended Aloha parameter e broadcast by the base station.
• the extended Aloha parameter e is set to 1, then the message to be sent is transmitted once in the next frame. If the parameter e is set to 2, then the message is transmitted in the next frame in the set (0,2,4,6,8,10,12,14), and is repeated in the frame immediately following that in which it was first transmitted, for example, if the current frame is 5, the message shall be transmitted in frames 6 and 7. If the parameter e is set to 4, then the message is transmitted in the next frame in the set (0,4,8.12), and the message is repeated in the three consecutive frames following that in which it was first transmitted, for example, if the current frame is 5, the message shall be transmitted in frames 8,9,10,11.
• the subscriber unit Following transmission of a message, the subscriber unit then listens to the broadcast channel for 16-e frames and compiles a valid Slot-List for the following multiframe, and selects one of the slots x at random in case a re-transmission is required. However, if
• the subscriber unit receives an acknowledgement message from the base station in the broadcast channel, then the subscriber unit takes
• a re-transmission counter is incremented each time the call set-up request is transmitted so as to monitor the number of re-transmissions.
• the call set-up request shall be transmitted in frames 8,9,10, 11.
• Base stations send slot list messages to subscriber units and manage slot lists dependent on the Carrier-lists they have stored for each associated subscriber unit. Where certain RF frequencies are designated as not to be used ('black'), the base station manages slot list messages so as to ensure that each subscriber unit always has an RF frequency available for use. In particular, at periods of high loading where selected classes of subscriber units are restricted from making calls, the base station operates to ensure that an Aloha slot will be available to a subscriber unit within a predetermined time period.
• the network has the following means of controlling access:
• PSTN Public Telephone Switched Network
• the level of usage in the network is monitored and calls are progressively restricted, as
• subscribers can be normal users, priority B users or priority A users as described above, each type of user having a different access priority. Subscribers sharing a subscriber unit can have different priorities.
• the highest threshold the last two channels are reserved for emergency calls only. Thus where there are say 60 channels (time slot/carrier frequency combinations), at a time of high loading the call set-up request for the 59th PSTN call at that time would be refused unless it is an emergency call.
• the number of reserved channels at the highest threshold can be other than two.
• the base station monitors, over time, the success of Public Switched Telephone Network (PSTN) calls and test calls on each RF frequency to each subscriber unit with which it communicates by radio.
• PSTN Public Switched Telephone Network
• an RF frequency is recategorised. For example, an RF frequency categorised as 'white' can be automatically reclassified as 'grey' should the frequency be unavailable for successful call transmission for more than a predetermined percentage of time. Conversely, 'grey' frequencies which are monitoried as becoming sufficiently reliable are re-categorised as 'white'.
• the updated Classified Carrier list for each subscriber unit is updated periodically.

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• Engineering & Computer Science (AREA)
• Computer Networks & Wireless Communication (AREA)
• Signal Processing (AREA)
• Mobile Radio Communication Systems (AREA)
• Transceivers (AREA)
• Iron Core Of Rotating Electric Machines (AREA)
• Selective Calling Equipment (AREA)
• Time-Division Multiplex Systems (AREA)
• Circuits Of Receivers In General (AREA)
• Radio Relay Systems (AREA)

Applications Claiming Priority (3)

Publications (1)

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ID=10761481

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• 1994
  • 1994-09-16 GB GB9418747A patent/GB9418747D0/en active Pending
• 1995
  • 1995-09-01 IL IL11515195A patent/IL115151A/xx not_active IP Right Cessation
  • 1995-09-01 IL IL11515095A patent/IL115150A/en not_active IP Right Cessation
  • 1995-09-08 MX MX9701972A patent/MX9701972A/es not_active Application Discontinuation
  • 1995-09-08 CN CN95195658A patent/CN1160473A/zh active Pending
  • 1995-09-08 JP JP8509976A patent/JPH10505965A/ja active Pending
  • 1995-09-08 BR BR9509340A patent/BR9509340A/pt not_active Application Discontinuation
  • 1995-09-08 WO PCT/GB1995/002133 patent/WO1996008939A1/en active IP Right Grant
  • 1995-09-08 BR BR9508942A patent/BR9508942A/pt not_active Application Discontinuation
  • 1995-09-08 JP JP8509981A patent/JPH10505968A/ja active Pending
  • 1995-09-08 EP EP95931284A patent/EP0781497B1/de not_active Expired - Lifetime
  • 1995-09-08 AT AT95931284T patent/ATE193631T1/de not_active IP Right Cessation
  • 1995-09-08 DE DE69517328T patent/DE69517328D1/de not_active Expired - Lifetime
  • 1995-09-08 AU AU34774/95A patent/AU3477495A/en not_active Abandoned
  • 1995-09-08 WO PCT/GB1995/002128 patent/WO1996008938A1/en not_active Application Discontinuation
  • 1995-09-08 MX MX9701976A patent/MX9701976A/es unknown
  • 1995-09-08 EP EP95931280A patent/EP0781496A1/de not_active Withdrawn
  • 1995-09-08 AU AU34778/95A patent/AU3477895A/en not_active Abandoned
  • 1995-09-14 ZA ZA957743A patent/ZA957743B/xx unknown
  • 1995-09-14 ZA ZA957742A patent/ZA957742B/xx unknown
• 1997
  • 1997-03-14 FI FI971095A patent/FI971095A/fi unknown
  • 1997-03-14 FI FI971096A patent/FI971096A/fi unknown

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