Telecommunications – Transmitter and receiver at separate stations – Plural transmitters or receivers
Reexamination Certificate
2000-06-30
2003-11-18
Trost, William (Department: 2683)
Telecommunications
Transmitter and receiver at separate stations
Plural transmitters or receivers
C455S436000, C455S439000, C455S442000, C455S525000
Reexamination Certificate
active
06650905
ABSTRACT:
TECHNICAL FIELD
The present invention relates to wireless networks and, more particularly, to power control of a downlink shared channel in the context of downlink transmit diversity.
BACKGROUND OF THE INVENTION
Universal Mobile Telecommunications System (UMTS) is to be the third generation mobile system, which is to offer higher data rates and a wide range of telecommunications services, including support for multimedia. UMTS will provide high-quality services with efficient use of network resources. UMTS is to be based on the Global System for Mobile communications (GSM) with some major modifications, e.g., a new radio interface. The UMTS network is to support both circuit-switched and packet-switched services. The circuit-switched technology will be based on the current GSM circuit-switched technology and the packet-switched technology on the General Packet Radio Service (GPRS), which is a new packet service for GSM.
The architecture of UMTS is thus to be based on GSM/GPRS. However, the access network part of UMTS will be new and revolutionary compared to GSM. The UMTS Terrestrial Radio Access (UTRA) Network (UTRAN) will be the new radio interface, which will be able to operate in two different modes: Wideband Code Division Multiple Access (WCDMA) and Time Division/Code Division Multiple Access (TD/CDMA). On the core network side, UMTS will consist of enhanced GSM-based circuit-switched and GPRS-based packet-switched core networks. UTRAN will have the ability to support multiple simultaneous connections for one user, i.e., simultaneous packet- and circuit-switched connections, and every connection can have individual properties, e.g., QoS (quality-of-service) parameters. Contrary to GPRS, UTRAN can also guarantee throughput for a packet-switched connection. This property is vital for some multi-media applications. Despite the wider bandwidth available in the UMTS system compared to GSM, the radio part of the system will remain the most susceptible to bottlenecks. As always, the design objective is an efficient use of limited resources without compromising versatility.
The UMTS packet network architecture will be highly similar to GPRS. However, the naming of some elements and interfaces has been changed from GPRS.
FIG. 1
shows the GPRS network architecture, and
FIG. 2
shows the UMTS packet network architecture. The UMTS packet network consists of the following network elements:
3G-SGSN: it will be the third generation version of the serving GPRS support node (SGSN).
3G-GGSN: it will be the third generation version of the gateway GPRS support node (GGSN).
HLR: it will be the GSM home location register (HLR) with some updates.
Node B: it will correspond to base transceiver station (BTS) in GSM.
RNC (Radio Network Controller): it will correspond to base station controller (BSC) in GSM.
The core network (CN) part of the packet-switched side will consist of 3G-SGSN, 3G-GGSN and HLR elements. The packet core network will include also the backbone network for connecting core network elements 3G-SGSN and 3G-GGSN together.
Node B and RNC will comprise the radio access network (RAN) part of the UMTS network. RAN will correspond to GSM's BSS (Base Station Subsystem). The responsibility of RAN is the handling of all radio-specific functions, e.g., radio channel ciphering, power control, radio bearer connection setup and release. The basic separation between elements will be that Node B will handle the physical layer functions, and RNC will handle the management functions. However, the separation might be slightly different than in GSM.
As can be seen by comparing
FIGS. 1 and 2
, the biggest architectural difference will be the new interface (Iur) inside RAN. It will reside between RNCs. In this connection, UMTS introduces a new concept called macrodiversity. In a macrodiversity situation, data will be sent via multiple Node Bs. Because signals will transferred via multiple routes over the air interface and combined in the MS and RNC, e.g., the fading effect will be less harmful, and thus lower power levels can be used. However, those Node Bs may belong to the area of two or more different RNCs, so the interface, i.e., Iur-interface between RNCs is required. In this situation, as shown in
FIG. 3
, the RNC can be in two logical roles. the RNC can be logically either a “drift” RNC (DRNC) or a “serving” (SRNC).
The actual termination point of the Iu-interface will be SRNC, as shown for both logical possibilities in FIG.
3
. The Iu-interface will connect the radio access network (RAN) and core network (CN), whether it be packet- or circuit-switched. SRNC will control information transfer and request radio resources from appropriate DRNCs. The DRNC will only relay information between the MS and SRNC, which is depicted in FIG.
3
.
Cell level mobility issues will be handled within UTRAN. When there exists a dedicated connection to the user equipment, the UTRAN will handle the radio interface mobility of the UE. This includes procedures such as soft handover.
For the new macrodiversity concept for 3G, it will be possible to set up multiple radio links simultaneously between a user equipment, for instance, a mobile station, in a wireless telecommunications system, in order to be in a position to decide which of the wireless links from a plurality of base stations is preferred at any given point in time during a communications session and to switch seamlessly between the radio links during the session depending on which link is preferred. In other words, a switch to a base station with a stronger signal can be made without having to set up a new connection. This means that the user equipment should be in a position to measure the magnitude of at least one parameter of the plural radio links simultaneously established between the user equipment and more than one of the plurality of base stations in order to periodically decide which one of the more than one of the plural radio links is currently preferred for use in the communications session between the user equipment and an end terminal connected to the system.
Thus, a soft handover is a category of handover procedures where the radio links are added and abandoned in such a manner that the user equipment (UE) always keeps at least one radio link to the UTRAN. For instance, as shown in
FIG. 4
, several Node B base stations (BS
1
, BS
2
, BS
3
) are illustrated in several corresponding cells. A user equipment in the form of a mobile station (MS) is shown moving from one cell to another. As the distance from base station
1
(BS
1
) increases, as illustrated in
FIG. 5
, the received signal strength from base station
1
at the mobile station decreases, while the received signal strength from base station
2
(BS
2
) increases. This is particularly noteworthy in a region of base station diversity shown as a distance window, with the signal strengths from base station
1
and base station
2
crossing over inside the window. Within a threshold region of signal strength, a soft handover can be effected, whereby the mobile station always keeps at least one radio link to the UTRAN effective. A This is distinguished from a hard handover, which would be a handover between different frequencies or between WCDMA and GSM (or a switch from FDD (Frequency Division Duplex) to TDD (Time Division Duplex) within UMTS).
It will be important for WCDMA power control to ensure that each user equipment receives and transmits just enough energy to properly convey information while interfering with other users no more than necessary. As shown in
FIG. 6
, several mobile stations (MS
1
, MS
2
, MS
3
, MS
4
) are shown communicating with a base station within a cell via corresponding radio links.
FIG. 7
shows received power at the base station (BS) without power control, and
FIG. 8
shows received power at the base station with optimal power control. In the downlink direction, a single mobile station sees the power levels of the whole transmission from the base station, and the power levels should in the ideal case vary as a function of the path loss in
Holma Harri
Toskala Antti
Miller Brandon J
Nokia Mobile Phones Ltd.
Trost William
Ware Fressola Van Der Sluys & Adolphson LLP
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