Multiplex communications – Communication over free space – Combining or distributing information via time channels
Reexamination Certificate
2000-11-15
2004-11-30
Vu, Huy D. (Department: 2665)
Multiplex communications
Communication over free space
Combining or distributing information via time channels
C370S328000, C455S522000
Reexamination Certificate
active
06826171
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
This application claims priority of European Patent Application No. 99309308.7, which was filed on Nov. 23, 1999.
FIELD OF THE INVENTION
This invention relates to mobile telecommunications systems, particularly though not exclusively the Universal Mobile Telecommunications System (UMTS).
DESCRIPTION OF THE RELATED ART
Packet transmission is a key feature of the UMTS as defined by the 3GPP™ standard. Methods to make the packet transmission efficient are required on both Downlink and Uplink. On the Downlink the radio access network has complete knowledge of how much, when, and to whom the packet transmissions are made. Hence a central control can be used for the Downlink packet transmission, for example, through a scheduler in the radio access network side to schedule the Downlink packet transmission.
For Uplink packet transmission where all mobile users are uncoordinated, a fully central controlled method (e.g., scheduling based method) on the Uplink is not feasible. There is therefore a procedure set forth in the MAC protocol specification for UMTS for gaining transmission access by making random packet transmissions on a random access channel (RACH) and detecting, according to a CDMA (Collision Detect Multiple Access) process, whether the packet transmission is received and acknowledged by the receiver. If the transmission is unsuccessful, the transmitter makes another attempt after a random time interval. The probability of gaining access is dependent on the number of other stations making transmissions, and, where a station is unsuccessful, the time interval for making another attempt is lengthened according to a persistency value, which is derived by the Radio Access Network from the traffic volume. Thus, Uplink packet transmission may be controlled through persistency broadcast on the Downlink to the User Equipment (UE). Persistency probability is updated and available for Uplink packet transmissions on the Random Access Channel and Common Packet Channel (RACH/CPCH).
Hence the principle of persistency control is that the radio access network monitors the Uplink traffic load and broadcasts a persistency value on the downlink Broadcast Control Channel. Based on the persistency broadcast information, UEs decide their (re) transmission probability, so that the packet access on RACH/CPCH is controlled.
The 3GPP Standard for UMTS is however silent as to the implementation of persistency control.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a practical and efficient persistency control algorithm for a mobile telecommunications system, based on specific measurement values provided by the system, and which avoids tedious computation.
In a first general aspect, the present invention provides, in a mobile telecommunications system, a method of determining a persistency value for making random transmissions for access to the system, the method comprising:
1. determining for a system cell, the maximum allowable user equipment transmission power P
MAX
; characterised by:
2. assessing the number, in a current time interval, of ongoing packet transmissions N
CURRENT
based upon a fraction a of measured current transmission power P
total
;
3. assessing the power available in a next time interval based upon the maximum allowable transmission power and the current transmission power, and determining therefrom a number of allowable new packets N
NEXT
in the next time interval; and
4. determining a persistency value p for transmission to user equipment in said cell, being a function of the number ongoing packet transmissions N
CURRENT
and said number of allowable new packets N
NEXT
.
In a second general aspect, the invention provides in a mobile telecommunications system, apparatus for determining a persistency value for making random transmissions for access to the system, the apparatus comprising:
means for providing for a system cell, the maximum allowable user equipment transmission power P
MAX
;
means for measuring user equipment current transmission power P
total
; characterised by:
means for assessing the number in a current time interval of ongoing packet transmissions N
CURRENT
based upon a fraction &agr; of measured current transmission power P
total
;
means for assessing the power available in a next time interval based upon the maximum allowable transmission power and the current transmission power, and determining therefrom a number of allowable new packets N
NEXT
in the next time interval; and
means for determining a persistency value p for transmission to user equipment in said cell, being a function of said number of ongoing packet transmissions N
CURRENT
and said number of allowable new packets N
NEXT
.
In a more specific aspect, the invention provides in the Universal Mobile Telecommunications System, a method of determining a persistency value for making random transmissions for access to the system, the method comprising;
1. determining for a system cell, the maximum allowable user equipment transmission power P
MAX
; characterised by:
2. assessing the number in a current time interval of ongoing packet transmissions N
CURRENT
based upon a fraction &agr; representing the user equipment measured current transmission power P
total
; wherein P
total
includes power from both packet Transport Channels (&agr;.P
total
) and power from circuit traffic Dedicated Transport Channels((1&agr;).P
total
.)
3. assessing the power available in a next time interval based upon the maximum allowable transmission power and the current transmission power, and determining therefrom a number of allowable new packets N
NEXT
in the next time interval; and
4. determining a persistency value p for transmission to user equipment in said cell, being a function of said number of ongoing packet transmissions N
CURRENT
and said number of allowable new packets N
NEXT
.
Said fraction &agr; may have any value of one or less than one. As preferred, said persistency value p is determined on the assumption that all ongoing packet transmissions N
CURRENT
will continue in the next time interval. Said persistency value p is preferably determined on the assumption that all ongoing packet transmissions N
CURRENT
and all said number of allowable new packets N
NEXT
have an equal possibility of transmission. In a preferred arrangement, the normalised persistency value p is equal to the inverse of the sum of said number in a current time interval of ongoing packet transmissions N
CURRENT
and said number of allowable new packets N
NEXT
. (note that p is normalised value.)
The number of ongoing packet transmissions N
CURRENT
is determined on the assumption that each packet is controlled to have the same power P
RACH
, whereby N
CURRENT
=&agr;.P
total
/P
RACH
. The number of allowable new packets N
NEXT
is determined on the assumption that each packet has the same power (at receiver side) P
RACH
, whereby N
NEXT
=(P
MAX
−P
total
)/P
RACH
. Thus, the persistency value p is given by P
RACH
(P
MAX
+(1−&agr;).P
total
)
−1
.
An overall persistency probability is transmitted over the system cell, having been determined as the product of the normalised persistency value p and the number n of total access channels available for packet transmission.
For the Universal Mobile Telecommunications System measured current transmission power P
total
includes power from both packet Transport Channels (&agr;·P
total
) and power from circuit traffic Dedicated Transport Channels((1−&agr;).P
total
.)
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M. Chuah, Q. Zhan, O. Yue, Access priorit
Bhatoolaul David Lahiri
Cao Qiang
Charriere Patrick
Lim Seau Sian
Mueckenheim Jens
Khuong Lee
Lucent Technologies - Inc.
Vu Huy D.
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