Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04J—MULTIPLEX COMMUNICATION
  • H04J3/00—Time-division multiplex systems
  • H04J3/02—Details
  • H04J3/06—Synchronising arrangements
  • H04J3/0602—Systems characterised by the synchronising information used
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B7/00—Radio transmission systems, i.e. using radiation field
  • H04B7/14—Relay systems
  • H04B7/15—Active relay systems
  • H04B7/204—Multiple access
  • H04B7/212—Time-division multiple access [TDMA]
  • H04B7/2121—Channels assignment to the different stations
  • H04B7/2123—Variable assignment, e.g. demand assignment
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B7/00—Radio transmission systems, i.e. using radiation field
  • H04B7/24—Radio transmission systems, i.e. using radiation field for communication between two or more posts
  • H04B7/26—Radio transmission systems, i.e. using radiation field for communication between two or more posts at least one of which is mobile
  • H04B7/2643—Radio transmission systems, i.e. using radiation field for communication between two or more posts at least one of which is mobile using time-division multiple access [TDMA]
  • H04B7/2659—Radio transmission systems, i.e. using radiation field for communication between two or more posts at least one of which is mobile using time-division multiple access [TDMA] for data rate control
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04J—MULTIPLEX COMMUNICATION
  • H04J3/00—Time-division multiplex systems
  • H04J3/02—Details
  • H04J3/06—Synchronising arrangements
  • H04J3/0602—Systems characterised by the synchronising information used
  • H04J3/0605—Special codes used as synchronising signal
  • H04J3/0608—Detectors therefor, e.g. correlators, state machines
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04J—MULTIPLEX COMMUNICATION
  • H04J3/00—Time-division multiplex systems
  • H04J3/16—Time-division multiplex systems in which the time allocation to individual channels within a transmission cycle is variable, e.g. to accommodate varying complexity of signals, to vary number of channels transmitted
  • H04J3/1694—Allocation of channels in TDM/TDMA networks, e.g. distributed multiplexers
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L47/00—Traffic control in data switching networks
  • H04L47/10—Flow control; Congestion control
  • H04L47/15—Flow control; Congestion control in relation to multipoint traffic
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L47/00—Traffic control in data switching networks
  • H04L47/10—Flow control; Congestion control
  • H04L47/30—Flow control; Congestion control in combination with information about buffer occupancy at either end or at transit nodes
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L47/00—Traffic control in data switching networks
  • H04L47/70—Admission control; Resource allocation
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L47/00—Traffic control in data switching networks
  • H04L47/70—Admission control; Resource allocation
  • H04L47/76—Admission control; Resource allocation using dynamic resource allocation, e.g. in-call renegotiation requested by the user or requested by the network in response to changing network conditions
  • H04L47/762—Admission control; Resource allocation using dynamic resource allocation, e.g. in-call renegotiation requested by the user or requested by the network in response to changing network conditions triggered by the network
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L47/00—Traffic control in data switching networks
  • H04L47/70—Admission control; Resource allocation
  • H04L47/82—Miscellaneous aspects
  • H04L47/824—Applicable to portable or mobile terminals
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L7/00—Arrangements for synchronising receiver with transmitter
  • H04L7/04—Speed or phase control by synchronisation signals
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L7/00—Arrangements for synchronising receiver with transmitter
  • H04L7/04—Speed or phase control by synchronisation signals
  • H04L7/041—Speed or phase control by synchronisation signals using special codes as synchronising signal
  • H04L7/042—Detectors therefor, e.g. correlators, state machines
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W28/00—Network traffic management; Network resource management
  • H04W28/02—Traffic management, e.g. flow control or congestion control
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04H—BROADCAST COMMUNICATION
  • H04H20/00—Arrangements for broadcast or for distribution combined with broadcast
  • H04H20/28—Arrangements for simultaneous broadcast of plural pieces of information
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W28/00—Network traffic management; Network resource management
  • H04W28/02—Traffic management, e.g. flow control or congestion control
  • H04W28/10—Flow control between communication endpoints
  • H04W28/14—Flow control between communication endpoints using intermediate storage
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W72/00—Local resource management
  • H04W72/50—Allocation or scheduling criteria for wireless resources
  • H04W72/54—Allocation or scheduling criteria for wireless resources based on quality criteria
  • H04W72/543—Allocation or scheduling criteria for wireless resources based on quality criteria based on requested quality, e.g. QoS

Definitions

• the present invention relates generally to wireless broadband technology and more particularly to dynamic allocation of bandwidth for point-to-multipoint systems.
• Point to multipoint (PTMP) systems such as wireless communication systems are constantly being demanded to accommodate more channels. This requires more efficient allocation of available limited bandwidth and scheduling of system resources and capacities.
• Wireless communication systems facilitate two-way communication between a plurality of subscriber radio stations or subscriber units (referred to as hub stations and remote stations).
• Example systems include mobile cellular telephone systems and personal communication systems (PCS).
• PCS personal communication systems
• the objective of many wireless communication systems is to provide communication channels on demand between the hub stations and the remote stations.
• frames of time are the basic transmission unit. Each frame is divided into a plurality of slots of time. Some time slots are used for control purposes and some time slots are used for information transfer. Information is typically transmitted during time slots in the frame, in which the time slots are specifically assigned. Transmissions from the hub station to the remote stations are often referred to as forward link transmissions. Transmissions from the remote stations to the hub station are commonly referred to as reverse link transmissions.
• Wireless communication systems typically use either time division duplexing
• TDD time division duplexing
• FDD frequency division duplexing
• Bandwidth requirements for PTMP systems vary as a function of time.
• the forward link and reverse link transmissions may have unequal or asymmetrical bandwidth requirements.
• the ratio of forward link/reverse link bandwidth desired may vary between stations and/or between channels.
• the need for symmetrical or asymmetrical communication in a channel varies depending upon the type of user/remote station.
• system resources/capacities should be efficiently scheduled to accommodate the increased demand for channels.
• many systems transmit information in accordance with priorities assigned to the information/data. That is, the highest priority data will be scheduled for transmission first before lower priority data is scheduled.
• a disadvantage of such a scheduling scheme is during times of heavy traffic congestion, lower priority lower priority data may not be scheduled within an allow amount of time if an abundance of highest priority data is to be scheduled.
• Another scheme is to schedule on a first in first out (FIFO) basis. However, this may lead to highest priority data not being scheduled/transmitted with an allowable amount time.
• Another disadvantage of current systems is they tend to have an inherent predetermined slant toward favoring the forward link transmissions over reverse link transmission.
• a technique for allocating bandwidth for a communications path of a point to multipoint (PTMP) system having a plurality of communications paths allocates available bandwidth within each communications path in accordance with a predetermined priority and an arrival time of information to be transmitted within the available bandwidth.
• PTMP point to multipoint
• Figure 1 is a stylized illustration of a PTMP system
• Figure 2 is an illustration of time division formatting in accordance with an embodiment of the present invention.
• Figure 3 is a diagram illustrating the relationship between hub stations, remote stations, and communication paths in accordance with an embodiment of the present invention
• Figure 4 is functional block diagram of a real time adaptive scheduling and bandwidth allocation system, in accordance with an embodiment of the present invention.
• Figure 5 is an illustration depicting centralized scheduling priority inversion
• Figure 6 is a functional block diagram of an exemplary inter-path scheduler in accordance with the present invention.
• Figure 7 is a flow diagram of an exemplary process for scheduling capacity and allocating bandwidth in accordance with an embodiment of the present invention.
• FIG. 1 is a stylized illustration of a PTMP system 100.
• System 100 comprises at least one hub station 24 and at least one remote station 22.
• a remote station 22 may comprise a local area network (LAN), such as depicted by LANs 26 and 28, individual processors, such as depicted by processor 30, a wireless communication means, such as facilitated by and depicted by antenna 32, an electromagnetic and/or optic communication means, such as facilitated by and depicted by conductor 34, or any combination thereof.
• LAN local area network
• processors such as depicted by processor 30
• a wireless communication means such as facilitated by and depicted by antenna 32
• an electromagnetic and/or optic communication means such as facilitated by and depicted by conductor 34, or any combination thereof.
• a hub station 24 may comprise a processor, such as depicted by processor 36, a wireless transmission means, such as facilitated by and depicted by antenna 38, an electromagnetic and/or optic communication means, such as facilitated by and depicted by conductor 34, or any combination thereof.
• antenna 38 comprises an omnidirectional antenna for achieving concurrent communication with all other stations. It is understood however, that antenna 38 may comprise a plurality of directional antennas. As shown by system 100, communication may be achieved between a plurality of hub stations 24, between hub stations 24 and remote stations 22, between a plurality of remote stations 22, or any combination thereof.
• TDM time-division multiplexing
• TDMA time-division multiple access
• a description of TDM and TDMA systems may be found in any of several textbooks pertaining to wireless communications, such as "Wireless Communications: Tdma versus Cdma", by Savo G. Glisic and Pentti A. Leppanen, June 1997; and "Wireless Communications & Networks", by William Stallings, August 23, 2001; for example.
• Figure 2 is an illustration of time division formatting in accordance with the present invention. As shown in Figure 2, a communication channel comprises a plurality of frames 42.
• Each frame 42 is partitioned into a forward link portion 44 and a reverse link portion 46.
• information is transmitted from a hub station (e.g., hub station 24) to at least one remote station (e.g., remote station 22).
• a reverse link 46 information is transmitted from the remote station(s) (e.g., remote station 22) to the corresponding hub station (e.g., hub station 24).
• Each of the forward link portions 44 and the reverse link portions 46 is divided into a plurality of time slots 48.
• the length of each time slot 48 is separately and dynamically reconfigurable in accordance with the demand for resources, including bandwidth, placed on the PTMP system (e.g., system 100).
• FIG. 3 is a diagram illustrating the relationship between hub stations 24, remote stations 22, and communication paths (CPs). Communication between each remote station 22 and a hub station 24 is accomplished via a communication path (CP). As shown in Figure 3, and described with reference to Figure 1, communication between stations may be accomplished via several types of media, such as an airlink, a vacuum, an electrical conductor, an optical conductor, or any combination thereof. In accordance with the system and method described herein, multiple communication paths (CPs) share and utilize the limited number of physical time slots typical in wireless TDM or TDMA architectures. These architectures may comprise various time division schemes, such as frequency division duplexing (FDD), time division duplexing (TDD), or any combination thereof, for example.
• FDD frequency division duplexing
• TDD time division duplexing
• a single CP is associated with communication between a hub station 24 and each remote station 22 of a wireless PTMP environment (e.g., system 100).
• a single CP is capable of supporting multiple application sessions concurrently, such as multiple Internet Protocol (IP) packet flows, and asynchronous transfer mode (ATM) virtual connections, for example.
• IP Internet Protocol
• ATM asynchronous transfer mode
• the exemplary configuration shown in Figure 3 comprises an ATM application utilizing 128 CPs.
• Each CP comprises a plurality of forward and reverse time divisions 48.
• Each ATM access point comprises N virtual connection (VC) terminations. It is understood that this configuration depicted in Figure 3 is exemplary.
• the number of CPs may be more or less than 128, the number of VCs associated with each multiplexer (MUX) may differ (i.e., not all equal to N), and the application may be other than asynchronous transfer mode (ATM), such as Internet Protocol (IP), precedence service and recent IP quality of service (QOS) enhancements, open systems interconnection (OSI), and multi protocol label switching (MPLS), for example.
• ATM asynchronous transfer mode
• IP Internet Protocol
• QOS IP quality of service
• OSI open systems interconnection
• MPLS multi protocol label switching
• Each PDU comprises a payload portion, and a prepended portion.
• the payload portion contains data indicative of the information to be transmitted and/or received.
• the prepended portion contains data indicative of the priority of the information and the amount of time a PDU has been waiting to be scheduled.
• the data in the prepended portion are updated dynamically and adaptively to provide scheduling and bandwidth allocation.
• the PDUs are scheduled in accordance with priorities assigned to the information, the amount of time a PDU has been waiting to be transmitted, and parameters associated with each CP.
• Information is assigned a priority, or multiple priorities, in accordance with a specific class-of-service.
• a class-of-service is a designation used to describe the service treatment and privileges given to a particular entity, such as a terminal or CP. For example, the highest priority may be assigned to information having a "time sensitive" COS, and lessor priorities may be assigned to information having either "not time sensitive” or "best effort" classes-of-service.
• Each CP supports a multiple, but limited, number of priority based classes-of- service (COS).
• Each CP is associated with parameters contained in a respective traffic management contract (TMC).
• TMC traffic management contract
• each CP may have its own unique TMC, all CPs may use the same TMC, or any combination thereof.
• Each TMC comprises parameters, which are utilized by the real time dynamic scheduling system to allocate capacity resources and bandwidth, and to select PDUs for transmission.
• a TMC is capable of being updated in real time.
• Each TMC contains parameters such as expected minimum and peak asymmetric transmission rates, maximum allowable delay increment for each class-of-service (COS), and discard delay threshold per COS, for example.
• each TMC comprises the attributes as described in Table 1.
• CP COS and TMC system and method are readily applicable to a plurality of wireless communications systems.
• the various ATM based quality of service (QOS) offerings may be grouped and/or mapped onto the CP priority based COS, and each CP's TMC may be updated in real time to reflect the sum of the minimum and peak ATM virtual connection (VC) rates that it supports.
• QOS quality of service
• VC virtual connection
• a TMC can be updated in real time, the transmission of both ATM permanent virtual connections (PVC) and switched virtual connections (SVC) may be supported.
• Capacity scheduling and bandwidth allocation utilizes inter-path scheduling and intra-path scheduling.
• Inter-path scheduling aids in determining the allocation of available capacity between multiple competing communications paths (CPs).
• Intra-path scheduling aids in determining PDU transmission within the context of a single CP direction.
• the inter-path scheduler 52 distributes bulk capacity grants to the forward path intra-path scheduler 54(a) and the reverse path intra-path scheduler 54(b).
• a bulk capacity grant comprises information indicative of the explicit number of PDUs, which may be transmitted in each direction within a specified transmission frame (also referred to as an airlink frame herein). This information is distributed to the remote stations 22 via airlink control channel signaling. In an exemplary embodiment, this information is distributed to remote stations 22 one airlink frame time in advance of actual implementation.
• each active instance of forward intra-path scheduling utilizes the bulk capacity grant provided by the inter-path scheduler 52 to make explicit PDU selections among the PDUs within its COS queuing mechanism.
• Intra-path scheduling utilizes an instantaneous priority calculation to make explicit PDU selections and then in turn generates a capacity report detailing the quantities of PDUs remaining queued within the CP for the given direction. This capacity report is provided as input into the path's bid processor 58.
• each active instance of reverse intra-path scheduling utilizes the bulk capacity grant provided by the inter-path scheduler 52 to make explicit PDU selections among the PDUs within its COS queuing mechanism.
• the intra- path scheduler 54 utilizes an instantaneous priority calculation to make explicit PDU selections and then in turn generates a capacity report detailing the quantities of PDUs remaining queued within the CP for the given direction. This capacity report is provided in an airlink reverse control-channel and is input into the path's bid processor 58.
• the path's bid processor 58 utilizes the capacity reports provided by the intra-path scheduler 54 to determine newly arrived PDUs that require consideration by the inter-path scheduler 52. These newly arriving PDUs are indicated to the inter-path scheduler 52.
• the inter- path scheduler 52 then utilizes the data associated with the newly arrived PDUs to redistribute the next bulk capacity grant, thus ensuring a system wide closed loop scheduling mechanism.
• Two instances or intra-path scheduling are implemented for each wireless CP.
• the distributed intra-path scheduler 54 prevents premature priority inversion and incremental delays of protocol data units (PDUs) due to centralized scheduling latency.
• PDUs protocol data units
• Figure 5 a priority 1 PDU has arrived at a remote location 22 after a priority 2 PDU has been previously bidded and granted capacity.
• the remote station 22 receives its grant of one (1) PDU, it is faced with a scheduling dilemma. It now has two PDUs to transmit and the one it has been granted capacity for is a lower priority and less delay sensitive than the later arriving, higher priority 1 PDU.
• An adaptive real time scheduler as described herein tends to prevent premature priority inversion and mitigate its adverse effects resulting from incremental delays of PDU transmission due to scheduling latency.
• the remote station 22 has the capability to ultimately decide which PDU to transmit in accordance with the bulk capacity grant.
• the priority 1 PDU of Figure 5 may be transmitted before the priority 2 PDU.
• the hub station (24) based inter-path scheduler 52 adapts its real time scheduling behavior to accommodate the distributed decisions being made by the intra-path schedulers 54.
• the intra-path scheduler 54 is a distributed dynamic priority based algorithm.
• the intra-path scheduler 54 schedules PDUs utilizing priority, while allowing controlled priority inversion when dictated by the parameters of the path's TMC. This attribute of the intra-path scheduler is referred to as dynamic delay-weighted prioritization (DDWP).
• the inter-path scheduler 54 performs prioritization based scheduling in accordance with delay sensitivities of the PDUs involved.
• the DDWP (intra-path) scheduler 54 comprises the capability to determine which PDU(s) will be transmitted in accordance with a bulk capacity grant from the associated inter-path scheduler 52.
• the intra-path scheduler 54 determines and assigns an instantaneous priority for each PDU at the front of each class-of-service transmission queue. This mechanism utilizes a time dependent instantaneous priority index that is then used in explicit PDU selections.
• the instantaneous priority for each PDU is determined in accordance with the following equation:
• t represents time
• P j (t) represents an instantaneous priority for a j th class-of-service as a function of time
• MDI j represents a communication path's maximum allowable delay increment for a j th class-of-service
• co,(t) represents a value indicative of the longest amount of time a PDU of a j tll class-of-service has been waiting for allocation.
• This instantaneous priority index, P,(t) is utilized to determine explicit inter-class PDU selection.
• DDWP dictates that the lower priority PDU is selected over the higher priority PDU.
• the CP is responsible for updating the inter-path scheduling function regarding any newly arrived PDU capacities that require scheduled capacity.
• the hub resident CP capacity bid processor 58 keeps a history of the path's PDU capacities per class-of-service. This history comprises counts of PDUs remaining queued within the CP the previous time it reported its queue capacities. These counts also include the counts of PDUs that have been granted by the inter-path scheduler 52 since the most recent capacity update.
• the CP's capacity bid function calculates any newly arriving capacities and reports these to the inter-path scheduler 52.
• the hub based capacity bid function continually adjusts to the actual reported queue quantities of the intra-path scheduling function. Thus by doing so, it continually synchronizes the centralized inter-path scheduling function to the distributed intra-path decision making processes.
• P ⁇ PREV becomes P ⁇ ACTUAL and P ⁇ GRANT becomes P ⁇ NEW .
• the path's bid function is rearmed for the next capacity report.
• a real time adaptive scheduling and bandwidth allocation system and method as described herein comprises one or more independent instances of inter-path scheduling.
• these instances are located at a hub station 24.
• These inter-path scheduling points may be one per carrier, one per carrier group, one per hub, or one instance may exist for a group of hubs.
• the inter-path scheduler 52 determines the asymmetric bulk capacity grants per CP under its oversight and is responsible for maintaining fairness among competing CPs.
• there is a one to many relationship (e.g., a 1:N relationship) between inter-path scheduling and intra-path scheduling as shown in Figure 6.
• Figure 6 is a functional block diagram of an exemplary inter-path scheduler.
• Intra-path capacity requests are submitted to the inter-path scheduler 52 in the form of PDU capacities.
• Each PDU submitted for scheduling is then assigned a priority indicator and queued in priority order within the appropriate class-of-service (COS) schedule.
• a priority indicator sort key is determined by the inter-path's Windowed Fair Priority Queuing (WFPQ) processor 62, which is used in determining CP and asymmetric fairness within each COS. WFPQ is described in more detail below.
• WFPQ Windowed Fair Priority Queuing
• the inter-path scheduler 52 utilizes a simple, fixed-priority processing scheme and converts the queued PDU schedules into CP bulk capacity grants each scheduling interval.
• the priority 1 schedule is processed until it is empty, proceeded by the priority 2 schedule, proceeded by the priority 3 schedule, etc., until the scheduling queues are empty or the scheduling interval's symbol and/or time budget expires. This process is repeated for each scheduling interval.
• the inter-path scheduler 52 determines fairness utilizing the attributes
• Inter-path capacities are scheduled with delay sensitivity by considering capacity allocations within the dominant domains of the CP COS (i.e., priorities) as depicted in Figure 6.
• inter-path scheduling accomplishes asymmetrical fairness, by utilizing an arrival time domain windowing scheme instead of a pure FIFO (first in first out) time stamp approach.
• This scheme treats all capacity requests occurring within the specified scheduling interval, called the arrival time domain window (ATTDW), as equally arriving at the same instance in time regardless of direction.
• ATTDW arrival time domain window
• the amount of capacity in each direction is also considered and used as part of the queuing algorithm's weighting.
• capacity grants slightly favor the predictive delay and asymmetry inherent within transmission queue capacities which are future predictors of capacity utilization. This increases scheduling efficiency by reacting to asymmetrical indications as early as possible.
• inter-path scheduling Other factors are also considered within inter-path scheduling to ensure fairness results within a mix of delay sensitive data streams. Such factors include the CP's asymmetric minimum and peak PDU capacity rates. For example, if one CP peak PDU rate is 2 times greater than another CP peak rate, fairness dictates that this be considered within the context of inter- path scheduling.
• each CP COS also has a maximum delay increment parameter within its TMC. All other things being equal (e.g., priority-classification, arrival time, queue capacity, and peak rates) the CP with the lower maximum delay increment attribute is favorably weighted. Due to these various weighting parameters that deal with priority, delay sensitivity, and fairness the inter-path scheduler 52 is referred to as utilizing windowed fair priority queuing (WFPQ).
• WFPQ windowed fair priority queuing
• the windowed fair priority queuing is used to schedule PDU transmissions at the inter-path level. It determines capacity allocations across the multiple communication paths (CPs) and it provides fair scheduling within a priority-based scheme.
• share based capacity allocations for lower priority high capacity remotes may disrupt the delay limits of higher priority PDU streams. This may occur within a fair share scheduling scheme because the path with the largest share of capacity also receives the lowest delay.
• a purely fixed priority scheduling scheme may be able to accommodate the delay bounds of the high priority PDU streams, but congestion within the higher priority PDU streams may result in periods of capacity starvation for lower priority PDU streams.
• Windowed fair priority queuing provides a combination of a fair share scheme with a priority based scheme.
• the windowed fair priority queuing (WFPQ) technique is used to assign scheduling priority within the context of multiple CPs across multiple classes-of-service. In such a mode of operation, during times of congestion, some delay may be introduced within the higher priority data streams to allow fair share allocations to the other classes-of-service.
• the WFPQ technique as presented herein is utilized independently for each class-of-service at the inter-path level. Thus, the WFPQ technique is used to assign scheduling priority within the context of each class-of-service independently.
• Inter-path fairness within windowed fair-priority queuing as described herein utilized a time domain window (TDW), wherein capacity requests are given an equivalent arrival time classification (AT TDW )-
• the arrival time is a function of the time domain window. For example, within a TDD or FDD framing structure using the framing interval as the time domain window, AT TDW is incremented for each framing interval. All other parameters being equal (e.g., same COS, peak rate, etc.), PDUs arriving earlier in time are prioritized and thus scheduled before PDUs arriving later in time.
• the communication path's current class-of-service queue capacity is also utilized in the scheduling prioritization process. This is because queue sizes are finite resources and all other things being equal (e.g., same COS, AT TD , etc.) the path with queues being stressed receive appropriate priority. Furthermore, indications of the upcoming direction of asymmetry may be predicted from the class-of-service queue capacities, which may be utilized to provide efficient our scheduling.
• the scheduling priority indicator is a function of priority within the time domain window (P TDW ) in accordance with the following equation;
• PTDW Hj + ATTDW + 1 PDUEsuClas. (2)
• P TDW is the scheduling priority indicator as a function of the time domain window
• TDW is the time domain window
• ⁇ j is the priority of the j ,h class-of-service
• AT TDW is the arrival time classification as a function of the time domain window
• 1/ PDU Est _ci ass is the reciprocal of the current estimated capacity of the particular class-of-service queue within the applicable communication path. The smaller the resultant values of P TDW the higher the priority.
• forward and reverse capacity requests receive corresponding treatment and scheduling priority as a function of the arrival time, class- of-service, and queue capacities.
• equation (2) as capacity builds in the resultant reverse link direction, asymmetry is weighted in the reverse link direction. This mechanism provides a forward look ahead tracking efficiency within asymmetrical capacity allocations.
• PDUs may accumulate in the airlink's distributed queuing mechanism resulting in arriving capacity requests that may have significant numbers of PDU capacities being requested. If the individual PDUs of capacity are not prioritized and scheduled in a distributed fashion proportional to their estimated arrival rate, large numbers (clumps) of lower rate capacities may distort the delay and peak rate requirements of higher rate communication paths.
• a first communication path may have a peak PDU rate of five (5) PDUs per airlink frame
• a second communication path may have a peak PDU rate of ten (10) PDUs per airlink frame
• each communication path request ten (10) PDUs within the same time domain window (TDW) and class-of-service.
• TDW time domain window
• MFSR TMC minimum frame service rate
• MDI maximum delay increments
• a single PDU schedule is queued for each PDU of capacity being requested (e.g., if a reverse link capacity request asks for 10 newly arrived asynchronous PDUs then 10 PDU schedules are queued).
• a PDU schedule contains a scheduling priority indicator (P P D U ) that is equivalent to the real number defined by the following equation.
• AT A dj is the per PDU arrival time adjustment. It is used to distribute scheduling priority among the individual PDUs as a function of the path's peak PDU rate which is directly proportional to its worst case arrival rate. Thus PDU capacity is scheduled at or better than the resultant arrival rate.
• the delay between their arrival, scheduling, and transmission is in part, a function of inherent airlink delay, over subscription, and the current congestion within the wireless transmission system.
• this distribution of schedule at peak rate between different communication paths results in a round robin-like attribute of fairness being inherently part of the hub's inter-path PDU scheduling.
• AT Adj increments from one (1) to the total number of new PDUs requested.
• Each instance of ATAdj is divided by the path's peak PDU rate to arrive at the specific PDUs arrival time adjustment. For example, if the path peak rate is 10 PDUs per airlink frame and 10 PDUs of capacity were requested, the resultant arrival time adjustments are calculated as follows: 0, 0. 1 , 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, and 0.9, respectively.
• TDW time domain window
• the Max-Del ayciass parameter is an inter-path scheduling adjustment increment that is provisional within each communication path's TMC. It is a unique parameter for each class-of-service. Thus, within the communication path, each class-of-service may have its own max delay increment (e.g., PI - MDI, P2 - MDI, etc.). Its use within the windowed fair priority queuing (WFPQ) technique provides provisional scheduling differentiation between competing communication paths. Thus, all other things being equal, the communication path with the lower maximum delay value, for the particular class-of-service, will be scheduled ahead of a communication path with a higher max delay tolerance, for the same class-of-service.
• WFPQ windowed fair priority queuing
• a set of PDU schedules is built and added to the appropriate class-of-service schedule queues every scheduling interval or time domain window.
• the fair priority queues are also be processed by the hub station's inter-path scheduler 52 every scheduling interval in P PDU priority order.
• the forward link transmission schedulers update their new PDU bids first and then the reverse link transmission schedulers update their new PDU bids.
• the PDU schedule queues represent a prioritized schedule that inherently defines the next TDD frame's asymmetrical symbol budget attributes.
• FIG. 7 is a flow diagram of an exemplary process for scheduling and allocating bandwidth.
• PDUs are formed at step 70 PDUs, as described previously, herein.
• Information to be communicated is segmented into fixed sized PDUs.
• Each PDU comprises a payload portion, and a prepended portion.
• the payload portion contains data indicative of the information to be transmitted and/or received.
• the prepended portion contains data indicative of the priority of the information and the amount of time a PDU has been waiting to be scheduled.
• the inter-path scheduler provides PDU bulk grants to each communication path at step 72, in accordance with an aggregate demand for resources and bandwidth by all remote stations 22, as described previously herein.
• PDU bulk grants are received by the intra-path scheduler at step 74, and PDUs are scheduled for transmission, for each communication path at step 76, in accordance with the description herein pertaining to equations (1) and (2) and associated text.
• capacity counts for each communication path/class-of-service are updated and provided to the inter-path scheduler for subsequent scheduling.
• the present invention may be embodied in the form of computer-implemented processes and apparatus for practicing those processes.
• the present invention may also be embodied in the form of computer program code embodied in tangible media, such as floppy diskettes, read only memories (ROMs), CD-ROMs, hard drives, high density disk, or any other computer-readable storage medium, wherein, when the computer program code is loaded into and executed by a computer, the computer becomes an apparatus for practicing the invention.
• the present invention may also be embodied in the form of computer program code, for example, whether stored in a storage medium, loaded into and/or executed by a computer, or transmitted over some transmission medium, such as over electrical wiring or cabling, through fiber optics, or via electromagnetic radiation, wherein, when the computer program code is loaded into and executed by a computer, the computer becomes an apparatus for practicing the invention.
• computer program code segments configure the processor to create specific logic circuits.

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