Patent Application
20070047553
It is becoming more important to be able to provide telecommunication services to subscribers which are relatively inexpensive as compared to cable and other land line technologies. Further, the increased use of mobile applications has resulted in much focus on developing wireless systems capable of delivering large amounts of data at relatively high speeds.
Development of more efficient and higher bandwidth wireless networks has become increasingly important and addressing issues of how to maximize efficiencies of such networks is an ongoing issue. One such issue relates to efficient scheduling of transmissions in the uplink direction (i.e., from subscriber stations (SS) to centralized access stations or base stations (BS)) while maintaining differentiated levels of service.
Aspects, features and advantages of embodiments of the present invention will become apparent from the following description of the invention in reference to the appended drawing in which like numerals denote like elements and in which:
While the following detailed description may describe example embodiments of the present invention in relation to broadband wireless metropolitan area networks (WMANs), the invention is not limited thereto and can be applied to other types of wireless networks where similar advantages may be obtained. Such networks specifically include, if applicable, wireless local area networks (WLANs), wireless personal area networks (WPANs) and/or wireless wide area networks (WWANs) such a cellular networks and the like. Further, while specific embodiments may be described in reference to wireless networks utilizing Orthogonal Frequency Division Multiplexing (OFDM) and/or Orthogonal Frequency Division Multiple Access (OFDMA) modulation, the embodiments of present invention are not limited thereto and, for example, can be implemented using other modulation and/or coding schemes where suitably applicable.
The following inventive embodiments may be used in a variety of applications including transmitters and receivers of a radio system, although the present invention is not limited in this respect. Radio systems specifically included within the scope of the present invention include, but are not limited to, network interface cards (NICs), network adaptors, fixed user stations, mobile stations, base stations, access points (APs), hybrid coordinators (HCs), gateways, bridges, hubs, routers and other network peripherals. Further, the radio systems within the scope of the invention may include cellular radiotelephone systems, satellite systems, personal communication systems (PCS), two-way radio systems and two-way pagers as well as computing devices including such radio systems such as personal computers (PCs) and related peripherals, personal digital assistants (PDAs), personal computing accessories, hand-held communication devices and all existing and future arising systems which may be related in nature and to which the principles of the inventive embodiments could be suitably applied.
Turning to
In the IEEE 802.16 standards the broadband wireless 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 IEEE 802.16 standards), two principle communicating wireless network nodes are defined including the Base Station (BS) (e.g., base station 115) and the Subscriber Station (SS) (e.g., subscriber stations 120, 122, 124).
In the example configuration of
In one implementation base station 115 sends data to subscriber stations 120-124 in downlink (DL) and receives data from stations 120-124 in uplink (UL) in form of radio frames. In one example embodiment, uplink and downlink communications are maintained by sending radio frames at constant, but configurable intervals (e.g. every 5 ms). One notable feature of these types of networks is that a single radio frame may consist of data destined to, or originating from, multiple subscriber stations. As an example, subscriber station 120 may service multiple connections for other devices of local area network 130 all within individual UL and/or DL radio frames.
Bandwidth in a radio link is often limited and thus, base station 115, as the managing entity, may control bandwidth utilization. For example, in downlink, base station 115 may analyze the amount of traffic incoming from provider network 110 and schedule it for transmission to destination subscriber stations, preferably in a fair and efficient manner. Managing base station 115 may also grant bandwidth to subscriber stations 120-124 for use in the uplink direction.
In one example configuration, uplink bandwidth is allocated per frame as a part of the UL or DL radio frame which can be used by a certain SS. If an SS has data to transmit in UL, it may explicitly requests UL bandwidth from the BS by specifying a transmit buffer occupancy for each connection it services.
Turning to
As has already been described, UL bandwidth may be allocated to each SS as part of an appropriate UL radio frame although the allocated parts are not necessarily continuous. Referring to
In certain implementations, one whole burst is typically allocated to a single subscriber station or a single connection of a subscriber station having more than one active connection. In the UL frame, several bursts, e.g., 310, 312 and 316, which are not necessarily adjacent, can be allocated to one subscriber station or connection, for example SS#1. Subscriber station MAC (Medium Access Control) PDUs (Protocol Data Units) 330 may be concatenated and MAC SDUs (Source Data Units) 340 fragmented to form shorter MAC PDUs 330 in an effort to more effectively use space available in bursts 310-316. However, not all connections support fragmentation of SDUs 340, for example, management messages on some management connections are not allowed to be fragmented. A subscriber station scheduler should take this into account when trying to find the best MAC PDUs 330 to match with each burst 310-316.
In various inventive embodiments, a subscriber station MAC scheduler will be responsible for scheduling data from all active connections for uplink transmission to a base station in a fair and efficient manner, appropriately prioritizing connections with respect to their QoS requirements and functions.
Accordingly, turning to
Critical management information should be transmitted on management connections, taking into account their management levels. Then the remaining uplink bandwidth may be divided among other connections, using appropriate scheduling services implied by the connection's traffic service class. For example, in the 802.16 networks, these types of traffic service classes may include: Unsolicited Grant Service (UGS), which is equivalent to constant bit rate, real-time (RT), non-real-time (nRT) or best effort (BE) traffic service classes. Each uplink connection can therefore be treated as a queue with a certain priority (e.g. RT queues have higher priority than nRT queues) and only UGS connections be treated as queues with strict servicing times (i.e., the highest priority queue).
According to various embodiments of the invention, efficient and robust subscriber station MAC scheduling algorithms or methods (e.g.,
The processes of the various inventive embodiments are intended to divide bandwidth granted to a particular subscriber station among all connections active in the station efficiently and in a fair manner, taking into account the service class and QoS requirements of each connection.
Depending on QoS requirements of connections active in subscriber station, data portions may be identified 410 sent are stored 420, 425 in two or more types of queues. In one embodiment, classes of data that does not require pre-grant UL bandwidth, such as data for a UGS connection, may be stored or identified 420 in a first (high priority) type of queue and classes of data which typically require an uplink bandwidth request and grant, such as data for RT, nRT and BE connections, may be stored or identified 425 in a second (lower priority) type of queue.
The subscriber station MAC scheduling process may then fill 430, 435 available UL bursts by polling these queues in a predetermined manner. For example, UGS connection queues may be polled in round robin (RR) fashion, while the type of queue set(s) are polled in weighted round robin fashion (WRR).
Filling available bursts according to the MAC subscriber station scheduling procedure 400 may be executed upon reception a bandwidth grant (defined as a number of UL bursts of variable length that the subscriber station can use to send its data) from the base station. Burst space may generally used to serve UGS queues first, for example on a round robin basis as described hereafter in reference to
In one non-limiting embodiment, referring to
When the queue is emptied 516, 524 the queue may be removed 530 from the list and the process is repeated for the next queue 538 on the list until all UGS connection queues are emptied 535. When all UGS queues are empty, process 500 may schedule 540 data in non-UGS type queues for uplink transmission.
Scheduling uplink data for non-UGS connections may include scheduling data in a weighted round robin fashion as mentioned previously in reference to
In one embodiment each queue for the queue set for these types of connections may be assigned a weight, which for example, may denote the largest portion of data that may be consumed in a single serving cycle (SC). The more demanding the QoS requirement for a connection, a correspondingly higher weight may be assigned for the respective queue. Accordingly, taking into account the weight of each queue, a serving cycle may be constructed. For example, SC={a,a,a,b,b,c} may mean that queue “a” has the highest priority (or weight) and will be served three consecutive times (e.g., three portions of data can be consumed). Subsequently, queue “b” would be served twice, and queue “c” (with the lower priority data) would be served once in the service cycle.
Turning to
If 604, after reserving 602 space for bandwidth requests, there are bursts available in the uplink grant, the next non-UGS queue in the serving cycle may be served 608. In one embodiment, a postponed data queue (PDQ) may be used to house data that was part of a previous service cycle but, for some reason was unable to be sent in the previous UL grant. For example, if a message that cannot be fragmented 612 and does not fit 614 in any of the remaining UL bursts, it may be placed 616 in the postponed data queue (PDQ). During the next execution of the scheduling process 600, messages from PDQ may be processed 606, 607 in the first order.
The queue being served, and that includes data which may be made to fit in available UL bursts, e.g., fragmented 612 or whole 614, is de-queued 618, 620 into the burst(s). If 622 data remains in any queues and there are no more available bursts 604, 624, a bandwidth request for all non-empty queues may be placed 626 in the reserved space 602. If 628, on the other hand, all queues are empty, the space reserved 602 for the bandwidth request may be released 630.
It should be recognized that the detailed processes 500, 600 for scheduling UL data are only examples of possible implementation of the inventive embodiments and that many variations are possible. For example, a serving cycle can be implemented as lists of queues to serve or the postponed data queue can be implemented as a set of markers specifying which queues should be temporarily handled with highest priority, etc. Thus generally speaking, any subscriber station uplink scheduling process which: (i) serves UGS connections before other connections; (ii) serves non-UGS connections in a weighted round robin fashion; (iii) provides initial burst allocation for bandwidth requests; or (iv) postpones data from some queues, may be considered within the scope of the inventive embodiments.
Referring to
In one example embodiment, RF interface 710 may be any component or combination of components adapted to send and receive multi-carrier modulated signals (e.g., OFDM) although the inventive embodiments are not limited to any specific over-the-air interface or modulation scheme. RF interface 710 may include, for example, a receiver 712, a transmitter 714 and a frequency synthesizer 716. Interface 710 may also include bias controls, a crystal oscillator and/or one or more antennas 718, 719 if desired. Furthermore, RF interface 710 may alternatively or additionally use external voltage-controlled oscillators (VCOs), surface acoustic wave filters, intermediate frequency (IF) filters and/or radio frequency (RF) filters as desired. Various RF interface designs and their operation are known in the art and the description thereof is therefore omitted.
In some embodiments interface 710 may be configured to be compatible with one or more of the IEEE 802.16 standards contemplated for broadband wireless networks, although the embodiments are not limited in this respect.
Processing portion 750 may communicate with RF interface 710 to process receive/transmit signals and may include, by way of example only, an analog-to-digital converter 752 for down converting received signals, a digital-to-analog converter 754 for up converting signals for transmission, and if desired, a baseband processor 756 for physical (PHY) link layer processing of respective receive/transmit signals. Processing portion 750 may also include or be comprised of a processing circuit 759 for medium access control (MAC)/data link layer processing.
In certain embodiments of the present invention, MAC processing circuit 759 may include an uplink scheduler 780, in combination with additional circuitry such as buffer memory 758, may function to queue, de-queue or otherwise schedule MAC SDUs for uplink transmission to a base station. Alternatively or in addition, baseband processing circuit 756 may share processing for certain of these functions or perform these processes independent of MAC processing circuit 759. MAC and PHY processing may also be integrated into a single circuit if desired.
Apparatus 700 may be, for example, a wireless mobile station, wireless router or NIC and/or network adaptor for computing devices. Accordingly, the previously described functions and/or specific configurations of apparatus 700 could be included or omitted as suitably desired.
Embodiments of apparatus 700 may be implemented using single input single output (SISO) architectures. However, as shown in
The components and features of station 700 may be implemented using any combination of discrete circuitry, application specific integrated circuits (ASICs), logic gates and/or single chip architectures. Further, the features of apparatus 700 may be implemented using microcontrollers, programmable logic arrays and/or microprocessors or any combination of the foregoing where suitably appropriate (collectively or individually referred to as “logic” or “circuit”).
It should be appreciated that the example station 700 shown in the block diagram of
Unless contrary to physical possibility, the inventors envision the methods described herein: (i) may be performed in any sequence and/or in any combination; and (ii) the components of respective embodiments may be combined in any manner.
Although there have been described example embodiments of this novel invention, many variations and modifications are possible without departing from the scope of the invention. Accordingly the inventive embodiments are not limited by the specific disclosure above, but rather should be limited only by the scope of the appended claims and their legal equivalents.
