Method of monitoring base stations with discontinuous...

Details Method of monitoring base stations with discontinuous... Method of monitoring base stations with discontinuous...

1999-08-08

2003-07-15

Vincent, David (Department: 2732)

Multiplex communications

Communication over free space

Combining or distributing information via time channels

C370S458000, C370S459000

Reexamination Certificate

active

06594250

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a method for monitoring BCCH carriers in GSM, and in particular to a method to control monitoring with discontinuous BCCH carriers in GSM.
BACKGROUND OF THE INVENTION
In recent years, mobile telecommunication systems have become increasingly popular based on usefulness and commonly availability. Moreover, a continued increase in the need for such systems and additional services associated therewith is expected for the near future.
One of the most widely spread and presently available mobile telecommunication systems is the so-called GSM system (“Groupe Speciale Mobile”) which meanwhile has become a common standard in European countries.
In general, in a mobile telecommunication system such as the GSM system, a mobile station MS, whether in a standby mode or in use, has to continuously communicate with a base transceiver station BTS or base station BS, respectively, in order to provide at any time the possibility to establish a radio link, i.e. to initiate or receive a call.
In connection with such a communication between the mobile station MS and the base station BS, information relating to the so-called radio link control process, like data necessary for control processes like power control (PC) of the used transmitters and handover (HO) of the mobile station MS from the currently associated base station BS to a neighbouring base station, are acquired, transmitted and evaluated. These above mentioned control processes performed in connection with the radio link control process are managed and effected by a so-called base station controller BSC superordinated to the base stations.
To this end, according to the GSM standard, the mobile station MS is required to monitor the received power levels of up to 32 neighbouring base stations BS and to transmit the received power levels of the six strongest neighbours and the corresponding signal quality to the base station BS it is presently allocated to.
Those measurements on the radio interface are effected for each radio link of a mobile station MS on a signalling channel and/or traffic channel associated to the respective mobile station MS, i. e. for each radio link between a mobile station and a base station BS it is presently allocated to and neighbouring base stations.
As to the transmission system according to GSM, it is distinguished between logic channels of different kinds, namely, between so-called traffic channels (TCH) and signalling channels also referred to as control channels (CCH).
Traffic channels (TCHS) are used for transmitting speech or data. The traffic channels have data rates of 13 kbit/s (full rate channel) or 6.5 kbit/s (half rate channel) for speech transmission, and a data rate between 2.4 kbit/s and 9.6 kbit/s for data transmission (at full rate) or up to 4.8 kbit/s (at half rate).
Control channels (CCHs) are used for transmitting control signals required for establishing and/or maintaining a radio link between the mobile station MS and the base station(s) BS. Among the control channels different types of control channels are distinguished, namely, e. g.
Broadcast CHannels (BCH),
Common Control CHannels (CCCH), and
Dedicated Control channels (DCCH).
Broadcast channels BCH are directed from a base station BS to a mobile station MS in a so-called downlink. Within a broadcast channel BCH it can be distinguished between
a Frequency Correction CHannel (FCCH) for frequency synchronization of the MS with the BS,
a Synchronization CHannel (SCH) for subsequently effecting a bit-synchronization of the MS with respect to the BS (i.e frame synchronization), and
a Broadcast Control Channel (BCCH) used for transmitting the basic information required by the mobile station MS for communication with the base station(s) BS. After all synchronizations have been effected, the MS can evaluate all received BCCH information necessary for the communication.
The Common Control CHannel (CCCH) is used for radio link establishment and includes a paging channel (PCH) and an access grant channel (AGCH) in downlink direction, and an random access channel (RACH) in uplink direction.
The dedicated control channels include a stand alone dedicated control channel (SDCCH) and an Associated Control CHannel (ACCH), the latter of which comprises the Fast Associated Control CHannel (FACCH) and the Slow Associated Control CHannel (SACCH), respectively accompanying a traffic channel TCH and used in connection with an assignment of a TCH or at handover (FACCH) or for measurement result transmission (SAACH).
The channels briefly described above each are logical channels which are mapped to physical channels of the GSM radio frequency band, respectively, with the GSM radio frequency band being divided in a downlink frequency band for BS to MS communications and an uplink frequency band for MS to BS communication.
Now, with respect to the data transmission method used on the respective (physical) channels, due to the fact that a mobile station MS uses only part time for transmitting/receiving of information and uses remaining time for effecting measurements of the kind briefly described above, a channel (carrier) assigned thereto is not continuously used by the mobile station MS for communication.
Therefore, a (physical) channel or carrier, respectively, has been made available to other stations for data transmission during the time (a first) mobile station MS effects measurements, by adopting the TDMA method (Time Divisional Multiple Access) for data transmission on the respective physical channel.
Thus, a mobile station uses a physical channel or carrier, respectively, intermittently, and the base station may communicate continuously with several mobile stations using a single carrier. Alternatively, a BS may communicate with several mobile stations MS using multiple carriers in a case of frequency hopping, for example.
To state this in greater detail, in mobile communication systems adopting the TDMA method a time-divisional communication takes place on the respective channel or carrier frequency, respectively, in consecutive so-called TDMA frames. A single TDMA frame consists of several so-called time slots TS of predetermined duration during which different contents of information referred to as a burst is transmitted. In particular, according to GSM standard, a time slot TS has a duration of 576,9 &mgr;s and eight consecutive time slots constitute a TDMA frame having a duration of 4.615 ms. Furthermore, the TDMA-frames consisting of eight time slots TS each are grouped to form multi-frames consisting of 51 TDMA-frames in case of a control channel CCH and 26 TDMA-frames in case of a traffic channel TCH.
The general concept of this conventional (Prior Art) hierarchy briefly described above is schematically depicted in
FIG. 1
of the accompanying drawings.
Within the respective time slots TS of the frames information is transmitted as the above mentioned so-called bursts. Five different types of bursts are defined, namely
normal burst NB
frequency correction burst FB
synchronization burst SB
dummy burst DB, and
access burst AB.
The FB, SB and AB burst, respectively, are bursts transmitted when a radio link is being established. After a link has been established, the further communication and exchange of information is effected using normal bursts. The dummy burst is transmitted when a transmission is not effected in all time slots of the BCCH carrier (the so-called beacon carrier).
Thus, one physical channel or carrier, respectively, supports a minimum number of at least 8 logical channels (1 logical channel corresponding to one time slot) (or 16 logical channels in case of the above mentioned half-rate transmission). Stated in other words, a single carrier supports a couple of connections. e. g. 8 connections, simultaneously, one for BCCH and the remaining for TCHs.
On the respective broadcast control channel BCCH general information concerning the base station is transmitted and the mobile station must measure the received power of the BCCH carrier of the neighbouring base stations and deco

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