Multiplex communications – Communication over free space – Repeater
Reexamination Certificate
1999-04-09
2003-01-14
Le, Thanh Cong (Department: 2684)
Multiplex communications
Communication over free space
Repeater
C370S347000, C370S503000, C455S422100, C455S436000
Reexamination Certificate
active
06507567
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to mobile communications, and more particularly, to the efficient allocation and use of resources in a mobile communications network.
BACKGROUND AND SUMMARY OF THE INVENTION
Current mobile telecommunications networks are typically designed to connect and function with Public Switched Telephone Networks (PSTNs) and Integrated Services Digital Networks (ISDNs). Both of these networks are circuit-switched networks and handle relatively narrow bandwidth traffic. However, packet-switched networks, such as the Internet, handle much wider bandwidth traffic. While wireline communication terminals, e.g., personal computers, are capable of utilizing the wider packet-switched network bandwidth, wireless mobile radio terminals are at a considerable disadvantage because of the relatively limited bandwidth of the radio/air interface that separates the mobile terminals from packet-switched networks. In the second generation Global System for Mobile communications (GSM) mobile communications system, a General Packet Radio Service (GPRS) was introduced to handle “bursty” traffic such as the infrequent transmission of e-mail messages, Internet information, and other data. Because GPRS is a packet-switching service, it only requires radio channel resources when data is actually being sent as compared to typically less efficient circuit-switched services that are reserved for a mobile user regardless of whether data is actually being sent. The GPRS packet-switched service enables the radio frequency spectrum to be more efficiently allocated across voice and data calls and allows channels to be shared between several users simultaneously.
Even though GSM provides both circuit-switched and packet-switched services to mobile users, GSM and other second generation mobile communication systems still suffer from narrow radio bandwidth. Radio access is needed that provides very high data rates and supports enhanced bearer services not realistically attainable with existing generation mobile communication systems. A third generation of mobile systems based on Wideband Code Division Multiple Access (W-CDMA) radio access is being introduced. Unlike narrow band access methods such as Frequency Division Multiple Access (FDMA) and Time Division Multiple Access (TDMA), and to some extent “regular” CDMA, W-CDMA currently supports 5 MHz to 15 MHz of bandwidth, and in the future, promises an even greater bandwidth. In addition to wide bandwidth, W-CDMA also improves the quality of service by providing robust operation in fading environments and transparent handovers between base stations (soft handover) and between base station sectors (softer handover). Multipath fading is used to advantage to enhance received signal quality, i.e., using a RAKE receiver and improved signal processing techniques, contrasted with narrow band mobile communications systems where fading substantially degrades signal quality.
Another limitation with the current GSM system is that it offers basically two categories of services: circuit-switched services through one particular type of network service node, such as a Mobile Switching Center (MSC) node, and packet-switched services offered through another type of network service node, such as a GPRS node. There is one set of channels for circuit-switched services and another different set of channels for packet-switched channels. There is not much flexibility to mix and match particular services to meet often changing needs of mobile subscribers. In contrast, the W-CDMA system provides a wide variety of services and enables flexible allocation of resources and delivery of requested services. Indeed, a single set of channels is used to support both circuit-switched and packet-switched services. Current needs for a particular service are analyzed, and then existing communication resources are flexibly and dynamically assigned taking into account current demands in the system for communications resources.
An example third generation, W-CDMA system, sometimes referred to as Universal Mobile Telecommunications System (UMTS) is shown in FIG.
1
. The UMTS
10
includes a representative, connection-oriented, external core network, shown as a cloud
12
, may be for example the PSTN or ISDN networks. A representative, connectionless-, external core network, shown as a cloud
14
, may be for example the Internet. Both core networks are coupled to a corresponding service node
16
. Core network
12
is connected to a connection-oriented service node shown as a mobile switching center node
18
which provides circuit-switched services. In the existing GSM model, the mobile switching center
18
is connected over an interface A to a Base Station System (BSS)
22
which in turn is connected to a radio base station
23
over an interface Abis. The Internet connectionless-network
14
is connected to a GPRS node
20
tailored to provide to packet-switched services. Each of the core network services
18
and
20
connects to a UMTS Terrestrial Radio Access Network (UTRAN)
24
over a Radio Access Network (RAN) interface. The UTRAN
24
includes plural Radio Network Controllers (RNCs)
26
. Each RNC
26
is connected to a plurality of base stations (BS)
28
and to any other RNCs in the UTRAN
24
. Radio communications between the base stations
28
and mobile stations (MSs)
30
are by way of a radio/air interface.
In the preferred example embodiment, radio access is based on WCDMA with individual radio channels being allocated using WCDMA spreading codes. The UTRAN
24
provides services to and from mobile stations over the radio interface for the external core networks
12
and
14
(and ultimately to external, core network end users) without then having to request specific radio resources necessary to provide those services. The UTRAN
24
essentially hides those details from the service nodes, external networks, and users. Instead, a “logical” radio access “bearer” is simply requested from UTRAN
24
by a service node
16
. A radio access bearer corresponds to the UTRAN service actually carrying user data through the UTRAN and over the radio interface. The term “connection” corresponds to the collection of all radio access bearers plus the control signaling associated with one particular mobile station.
It is the task of the UTRAN
24
to map the mobile connection onto physical transport channels in a flexible, efficient, and optimal manner. Thus, each service node simply requests one or more radio access bearers with a mobile station where each bearer may have an associated quality of service. Quality of service may include for example a desired bit rate, an amount of delay before information is transferred, a minimum bit error rate, etc. The UTRAN
24
, in response to radio access request to support a connection, assigns transmission resources (e.g., an ATM transport connection) through the UTRAN
24
and a radio channel (e.g., a spreading code) over the radio interface.
In mapping a radio access connection onto one or more specific radio channels, the UTRAN
24
flexibly balances and optimizes a number of parameters including quality of service, range (distance between mobile station and base station), traffic load-capacity, and mobile station transmission power. One of two different types of radio channels may be selected by the RNC
26
to support a mobile connection: a dedicated or a common channel. The two radio channel types differ by the degree of radio resource reservation per channel. For a dedicated radio channel, resources in terms of spreading code(s) and power/interference are allocated to this particular mobile station. A common radio channel is a resource (spreading code) that is shared dynamically between multiple mobile stations. Based on the requested quality of service and the current traffic conditions, the RNC
26
may select the type of radio channel to carry the information associated with the radio access bearer service request.
As an example, if high quality of service with low delay guarantee is required, the RNC
26
ma
Cong Le Thanh
Nixon & Vanderhye P.C.
Telefonaktiebolaget LM Ericsson (publ)
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