Developments in a number of different digital technologies have greatly increased the need to transfer data from one device across a network to another system. Technological developments permit digitization and compression of large amounts of voice, video, imaging, and data information, which may be transmitted from laptops and other digital equipment to other devices within the network. These developments in digital technology have stimulated a need to deliver and supply data to these processing units.
It is becoming increasingly attractive to use wireless nodes in a wireless network as relaying points to extend range and/or reduce costs of a wireless network. A Multi-hop Relay (MR) network may use fixed and/or mobile stations as relaying points to optimize communications and increase the efficiency of transmissions. One notable issue is how to coordinate the selection of optimal transmission paths using new protocols and architectures and reduce costs associated with these networks.
The subject matter regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. The invention, however, both as to organization and method of operation, together with objects, features, and advantages thereof, may best be understood by reference to the following detailed description when read with the accompanying drawings in which:
It will be appreciated that for simplicity and clarity of illustration, elements illustrated in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity. Further, where considered appropriate, reference numerals have been repeated among the figures to indicate corresponding or analogous elements.
In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be understood by those skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, components and circuits have not been described in detail so as not to obscure the present invention.
Wireless multi-hop relay systems have become the focus of several current standardization efforts. For example, for WLANs the Institute of Electrical and Electronics Engineers (IEEE) 802.11s Mesh Task Group (TG) is actively working on standard solutions for WLAN mesh networking. Additionally, the IEEE 802.16j Multi-hop Relay (MR) task group is also evaluating solutions for standardization in furtherance of the IEEE 802.16j project approval request for wireless broadband access (WBA) networks.
The multi-hop relay systems provide a cost effective way for multi-media traffic to increase in range. The relay stations offer extended coverage through existing networks and the MR system is a cost effective solution accommodating many mobile subscribers, establishing wide area coverage and providing higher data rates. Thus, the multi-hop relay systems enhance throughput and capacity for 802.16 systems and enable rapid deployment which reduces the cost of system operation.
MR relay stations are intended to be fully backward compatible in the sense that they should operate seamlessly with existing 802.16e subscriber stations. A further phase of 802.16 is expected to introduce enhanced relay and WBA subscriber stations designed for use in MR networks. While the embodiments discussed herein may refer to 802.16 wireless broadband access networks, sometimes referred to as WiMAX, an acronym that stands for Worldwide Interoperability for Microwave Access, which is a certification mark for products that pass conformity and interoperability tests for the IEEE 802.16 standards, they are not so limited and may be applicable to WLAN, other types of mesh networks or even combinations of different networks. Multi-hop relay techniques may be applied to other emerging standards such as 3rd Generation Partnership Project (3GPP) for the Long Term Evolution (LTE).
Relay Stations (RSs) 140 and 150 wirelessly communicate and relay messages in MR network 100 using wireless protocols and/or techniques compatible with one or more of the various 802 wireless standards for WPANs and/or standards for WMANs, although the inventive embodiments are not limited in this respect. As illustrated in the figure, Relay Stations (RSs) 140 and 150 provide access to Mobile Stations 130 and 180 as well as relay data on behalf of other RSs. In certain non-limiting example implementations of the inventive embodiments, the topology illustrated is tree-like with the MR-BS at the root and MSs at the leaves to provide multiple communication paths or links. Access links provide the supported paths between the MR-BS and the MS and further between the RS and the MS. Relay links provide the support paths between the MR-BS and the RSs.
MR network 100 may be comprised of several macro cells, each of which may generally comprise at least one base station similar to MR base station 110 and a plurality of relay stations similar to RSs 140 and 150 dispersed throughout each macro cell and working in combination with the base station(s) to provide a full range of coverage to client stations. The multi-hop topology between MR-BS 110 and RSs 140 and 150 can be viewed as a Point-to-Multipoint (PMP) link. Further, RS 140 is connected to RS 160 and RS 170 via a PMP link, where each PMP link relies on the stations to maintain time and frequency synchronization that is performed via the broadcast and reception of a downlink (DL) preamble, whereas uplink (UL) synchronization is performed by a ranging process.
MR network 100 utilizes a frame structure which allows multiple relay links to share a channel, and thus, multiple PMP links may be supported on the same channel. When multiple PMP links share a channel, the stations that participate in the links synchronize and data is transmitted to minimize interference. The frame structure is configurable to optimize the topology and the requirements for deployment and allow the multiple PMP links to share the channel while utilizing a combination of time division multiplexing (TDM) and spatial reuse.
The number of RSs included in multi-hop network 100 may be dynamically changed as part of the frequency planning and deployment process. Frame structure 300 may be adjusted accordingly during operation of the system to include the appropriate phases for these stations. Frame structure 300 allows access and relay links to share a channel in TDM fashion by partitioning the access and relay links into separate groups, where each group is assigned to a phase. All RSs that are DL stations in a phase transmit their preamble in the DL portion of that phase. All preambles within a phase are transmitted in the same symbol, so assigning two RSs to be DL stations in a phase causes them to transmit their preambles at the same time.
The interleaved frame structure not only enables the sharing of a channel between relay and access links, but further provides the ability to transmit a packet across a 2-hop path within one frame if the processing at the RS is sufficient. An n-hop link exists if an MR-BS and an MS is separated by n-1 RSs, or alternatively, if an MR-BS and a SS is separated by n-1 RSs. In general, packets traversing multiple hops may experience increased packet delays which may reduce the Quality of Service (QoS) of the system. However, frame structure 300 enables relays to mitigate any increased packet delay which improves the QoS for a 2-hop link.
In the UL subframe the interleaved frame structure provides time slots that schedule packet information travel from an MS to its MR-BS within one frame. During the ACCESS LINK UL (slot 318 shown in
By way of example, 90% of MR deployment contains 2-hop links only. In these deployment situations interleaved frame structure 300 would improve the QoS of approximately 90% of the users in the MR deployment. In general, interleaved frame structure 300 may avoid introducing an extra delay of 1 frame for an n-hop link based on the following satisfied conditions: the number of relay phases M>(n-1) for an n-hop link; stations are assigned to a correct phase; the processing at the RS is sufficient to turn around packet information to retransmit; and allocation is available that allows the RS to transmit what it receives from the uplink/downlink to the downlink/uplink. The correct RS product design and a 2-hop link may satisfy the conditions for taking advantage of interleaved frame structure 300.
By now it should be apparent that the interleaved frame structure provides the ability for the access and relay links to share a single channel and enable the transmission of packets across a 2-hop path within one frame. Specifically, the interleaved frame structure in combination with fast processing at the RS allows scheduled packet information to travel from an MS to its MR-BS within one frame.
While certain features of the invention have been illustrated and described herein, many modifications, substitutions, changes, and equivalents will now occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.
The present application claims priority to U.S. patent application Ser. No. 60/854,470, filed Oct. 25, 2006, entitled “Interleaved Frame Structure Enabling Relay and Access Links to Share a Channel for Multi-Hop Wireless Broadband Access Communications,” the entire disclosure of which is hereby incorporated by reference in its entirety.
Number | Date | Country | |
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60854470 | Oct 2006 | US |