Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
2000-11-16
2004-05-18
Gary, Erika (Department: 2681)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S450000, C455S561000
Reexamination Certificate
active
06738624
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
This invention relates generally to communication within a mobile telecommunications system, and more particularly this invention relates to communication between a base station (Node B) and a radio network controller (RNC) in order to enhance call control and resource management.
BACKGROUND ART
The telecommunications industry is in the process of developing a new generation of flexible and affordable communications that includes high-speed access while also supporting broadband services. Many features of the third generation mobile telecommunications system have already been established, but many other features have yet to be perfected.
One of the most important systems within the third generation of mobile communications is the Universal Mobile Telecommunications System (UMTS) which will deliver voice, data, multimedia, and wideband information to stationary as well as mobile customers. UMTS is designed to accommodate increased system capacity and data capability (UMTS is synonymous with WCDMA or wideband code division multiple access). Efficient use of the electromagnetic spectrum is vital in UMTS. It is known that spectrum efficiency can be attained using frequency division duplex (FDD) or with time division duplex (TDD) schemes, and these schemes can be employed in the context of UMTS and WCDMA.
As can be seen in
FIG. 1
, the UMTS architecture consists of user equipment
102
(UE), the UMTS Terrestrial Radio Access Network
104
(UTRAN), and the Core Network
126
(CN). The air interface between the UTRAN and the UE is called Uu, and the interface between the UTRAN and the Core Network is called Iu.
The UTRAN consists of a set of Radio Network Subsystems
128
(RNS), each of which has geographic coverage of a number of cells
110
(C), as can be seen in FIG.
1
. The interface between the subsystems is called lur.
Each Radio Network Subsystem
128
(RNS) includes a Radio Network Controller
112
(RNC) and at least one Node B
114
, each Node B having geographic coverage of at least one cell
110
. As can be seen from
FIG. 1
, the interface between an RNC
112
and a Node B
114
is called Iub, and the Iub is hard-wired rather than being an air interface. For any Node B
114
there is only one RNC
112
. A Node B
114
is responsible for radio transmission and reception to and from the UE
102
(Node B antennas can typically be seen atop towers or preferably at less visible locations). The RNC
112
has overall control of the logical resources of each Node B
114
within the RNS
128
, and the RNC
112
is also responsible for handover decisions which entail switching a call from one cell to another or between radio channels in the same cell.
The FDD method uses separate frequency bands for uplink and downlink transmissions over the Uu interface (i.e. over the air interface between UTRAN
104
and the User Equipment
102
). In contrast, the TDD method allocates different time slots (compared to different frequencies) for these uplink and downlink communications. Generally, TDD is very flexible regarding the allocation of time slots, and therefore is very well-suited to applications that are asymmetric with respect to uplink and downlink data volume (e.g. web browsing entails a much higher downlink than uplink data volume). Combining FDD and TDD modes provides maximum efficiency and flexibility for third generation networks.
In order for the RNC
112
to provide effective call control and resource management to each Node B
114
, it must receive information from the Node B
114
about Node B's time-dependent resources. The problem of obtaining appropriate resource information from Node B
114
has not been adequately addressed by the related art, especially with regard to TDD (as compared to FDD), and therefore the ability of an RNC
112
to provide call control and resource management has suffered.
A particularly important piece of information for the RNC
112
to receive is information about the currently available processing capacity at Node B
114
. Processing capacity is to be distinguished from air interface capacity. Air interface capacity is limited by factors such as noise and interference, whereas processing capacity refers to the capacity of the Node B
114
itself to process calls. When the RNC
112
does not accurately know the processing capacity of Node B
114
that is currently available, it is very difficult or impossible for the RNC
112
to accurately allocate call traffic to the Node B
114
.
It is important to understand that the processing capacity at Node B
114
varies from time to time even if the number of user equipments
102
(UE) remains the same. This variation is due to the fact that the required processing per UE
102
depends upon how the logical resources of Node B resources are used for each of the particular UEs. The required processing for a particular user can depend upon what kind of coding a user has, how many multicodes are involved, how the users are divided in different time slots (TDD only), the number of users involved in a handover (FDD only), how the user's data stream is divided if there are multiple channel elements, the quality of service assigned to a call, et cetera. Thus, it is not adequate for the RNC
112
to simply know the number of UE's that a Node B
114
is handling, because each Node B
114
may require a different type of implementation. Rather, the RNC
112
should ideally receive from the Node B
114
, over the Iub interface, a simple and accurate measure of the Node B's available processing capacity without any need for specifying the particular implementations that Node B
114
is providing to each UE
102
. In TDD, no adequate solution to this problem has been developed. In FDD, the problem has been partially addressed by using the spreading factor of Node B
114
as an indicator of processing capacity, and reporting this spreading factor over the Iub.
With WCDMA, information bits are spread over an artificially broadened bandwidth. This task is accomplished by multiplying the bits, using a pseudorandom bit stream. The bits in the pseudorandom bit stream are referred to as chips, so the stream is known as a chipping, or spreading, code. This spreading increases the bit-rate of the signal, and increases the amount of bandwidth occupied by the signal, by a ratio known as the spreading factor, namely, the ratio of the chip rate to the original information rate.
The spreading factor can be used with limited success to indicate processing capacity in FDD, but the spreading factor is almost completely insufficient in TDD, because the TDD spreading factor is substantially constant in the downlink to the UE
102
, and furthermore the TDD spreading factor range is very narrow as compared with the FDD spreading factor range (e.g. 1-16 in TDD as compared with 4-512 in FDD). In particular cases, the spreading factor might vary between two values in TDD, but such a rough measurement would not allow the RNC
112
to meaningfully model the processing capacity of Node B
114
, and thus the processing capacity parameter is currently undefined in TDD. Even in FDD, using the spreading factor is not an ideal solution, because the FDD spreading factor becomes imprecise at the start of the 4-512 scale (e.g. the spreading factor between 4 and 8 corresponds to a very large difference in processing capacity).
Information about the use of the spreading factor as an indicator of FDD processing capacity can be found, for example, in publications of the 3
rd
Generation Partnership Project (3GPP). In particular, 3GPP TS 25.433 “UTRAN Iub Interface NBAP Signaling” (Version 3.3.0, September 2000) describes how the RNC
112
audits resources at the Node B
114
, which then reports processing capacity by way of an audit response (section 8.2.7). The 3GPP TS 25.433 publication also describes how the Node B
114
may report to the RNC
112
at the Node B's own initiative by way of a resource status indication (section 8.2.15). These are the only two instances in which the prior art
Aksentijevic Mirko
Hwang Woonhee
Toskala Antti
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