CA2349115A1 - Method and apparatus for dynamic bandwidth allocation to minimize fragmentation of data packets in a broadband wireless access system that provides voice, data and multimedia services - Google Patents
Method and apparatus for dynamic bandwidth allocation to minimize fragmentation of data packets in a broadband wireless access system that provides voice, data and multimedia services Download PDFInfo
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- CA2349115A1 CA2349115A1 CA002349115A CA2349115A CA2349115A1 CA 2349115 A1 CA2349115 A1 CA 2349115A1 CA 002349115 A CA002349115 A CA 002349115A CA 2349115 A CA2349115 A CA 2349115A CA 2349115 A1 CA2349115 A1 CA 2349115A1
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W28/00—Network traffic management; Network resource management
- H04W28/16—Central resource management; Negotiation of resources or communication parameters, e.g. negotiating bandwidth or QoS [Quality of Service]
- H04W28/26—Resource reservation
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- 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
- H04W28/06—Optimizing the usage of the radio link, e.g. header compression, information sizing, discarding information
- H04W28/065—Optimizing the usage of the radio link, e.g. header compression, information sizing, discarding information using assembly or disassembly of packets
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W72/00—Local resource management
- H04W72/04—Wireless resource allocation
- H04W72/044—Wireless resource allocation based on the type of the allocated resource
- H04W72/0446—Resources in time domain, e.g. slots or frames
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W72/00—Local resource management
- H04W72/12—Wireless traffic scheduling
- H04W72/1263—Mapping of traffic onto schedule, e.g. scheduled allocation or multiplexing of flows
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W72/00—Local resource management
- H04W72/20—Control channels or signalling for resource management
- H04W72/23—Control channels or signalling for resource management in the downlink direction of a wireless link, i.e. towards a terminal
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W72/00—Local resource management
- H04W72/50—Allocation or scheduling criteria for wireless resources
- H04W72/52—Allocation or scheduling criteria for wireless resources based on load
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W88/00—Devices specially adapted for wireless communication networks, e.g. terminals, base stations or access point devices
- H04W88/08—Access point devices
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- Computer Networks & Wireless Communication (AREA)
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Abstract
A method of dynamically allocating bandwidth of a communications channel for different types of communications traffic is disclosed. The transmission system includes a base station that communicates with access stations via a broadband wireless access network, in which the base station transmits information to the access stations via downstream channels and the access stations transmit information to the base station via upstream channels. The communication mechanism that uses an access protocol is modified to provide allocation of a variable number of voice slots and a variable number of data slots in each frame. The base station dynamically adjusts the location of slots for different types of communications traffic. For example, voice traffic from different access stations allocated back-to-back results in bigger data slots. As a result, this dynamic relocation of slots minimizes fragmentation of data packets to enhance base station and access stations efficiencies and to enhance upstream capacity.
Description
METHOD AND APPARATUS FOR DYNAMIC BANDWIDTH ALLOCATION TO
MIT~VIIZE FRAGMENTATION OF DATA PACKETS IN A BROADBAND
WIRELESS ACCESS SYSTEM THAT PROVIDES VOICE, DATA AND
MULTIMEDIA SERVICES
FIELD OF THE INVENTION
The present invention relates generally t.o the media access control protocol applied to a bi-directional communications medium, such as a Broadband Wireless Access system where competing access stations are connected via a bro;~dband wireless network to a common base station, to communicate different types of information, or traffic, such as voice, data, or control information. This invention also relates to bi-directional hybrid fibencoax networks, which are akin to broadband wireless access networks in offering a wide range of telecommunication services to residences and businesses.
BACKGROUND OF THE INVENTION
Currently a great deal of activity is directed towards broadband wireless access networks to connect multiple residential and business users using wireless systems in order to provide new interactive multimedia services, including telephony and data networking. The present invention is related to establish an upstream MAC (Me~3ia Access Control] protocol in the controller of the base station such that bandwidth is dynamically allocated for a mix of interactive and non-interactive traffic types. The conventional LAN protocols, for example CSMA/CD and R-ALOHA protocols, are not suitable for use in wireless systems because the wireless networks have separate upstream and downstream channels, and the subscribers can only listen to the downstream from the base station and transmit in the allocated upstream.
The subscribers cannot listen directly tca the upstream transmissions from other subscribers, and are therefore incapable of coordinating their' transmissions by themselves. Usage of the upstream is centrally managed in the base station.
Many media access protocols have been proposed. The Data-Over-Cable Service Interface Specification (DOCSI~~) standard has been initially developed by CATV
operators and CableLabs. This specification has begun. to find a home outside the TV market. Specifically, a group of companies formed a consortium, called the Wireless DSL Consortium, to produce an enhanced version of the standard for broadband wireless applications, and are currently under study by the IEEE
802.16 committee.
The upstream channel is modeled as a stream of mini-slots. Protocols have been proposed to describe the elements of requesting, granting, and using the upstream bandwidth. The basic mechanism for assigning bandwidth is the bandwidth allocation MAl' which describes the uses to which the upstream mini-slots must be put, and through which the base station controls access to these slots by the access stations. Many numbers of contiguous. slots may be granted to an access station to transmit data. A larger MAC PDU may need to be fragmented into smaller pieces that are individually transmitted and then reassembled at the base station.
The main objective of this inventic7n is to provide an optimum method of bandwidth allocation in a transmission system, and in particular in a. broadband wireless access network, such that the fragmentation of data packets is minimized to improve system performance while not introducing an additional delay and fitter into the real-time traffic.
SUMMARY OF THE INVENTION
Although there arc: protocols available that provide mechanisms for bandwidth allocation for multimedia traffic types, we propose another way to optimize the efficiency of bandwidth allocation in an access protocol that also minimizes the need for the fragmentation of larger data packets. In particular, and in accordance with achieving the objective of the present invention, a base station communicates to access stations via a broadband wireless access network using a media access control protocol, which is modified to support a variable number of voice mini-slots and a variable number of data mini-slots in each frame.
The base station dynamically adjusts the positioning of mini-slots over a period time for on-line voice traffic in order to reduce its random distribution and random availability of free mini-slots to be used for other traffic types. As a result, the inventive; concept allows the base station to efficiently utilize remaining bandwidth on the communications channel for data traffic by minimizing their fragmentation. It should be noted that the fragmentation introduces overhead by adding extra fragmentation header, and costs more memory and CPU cycles for the packet assembly and disassembly functions. For example, the number of times all larger data packets are fragmented will introduce a bandwidth overhead at least equal to the product of this number and the fragmentation overhead. The objective of the present invention is to minimize the addition of this fragmentation overhead by minimizing the need for fragmentation.
In an embodiment of the invention, a base station communicates to access stations via a broadband wireless access network using the conventional DOCSIS based media access control protocol, which is modified to dynamically allocate bandwidth such that the on-line voice traffic mini-slots are positioned back-to-back and the remaining mini-slots. can service larger data packets without fragmentation. Any presence of voice silence reflects in its mini-slat being dynamically utilized for other traffic types and affects the size of contiguous data slots available to service best effort traffic. For example, less voice slots provide larger data slots to service larger data traffic.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 illustrates an exemplary arrangement of a broadband wireless access network utilized in accordance with the present invention, the network connecting a base station to a plurality of access stations for downstream signal broadcasting and allowing upstream information transmission from the individual access statians to the base station as well;
--2_ DETAILED DESCRIPTION OF THE INVENTION
The present invention encompasses a system utilizing a broadband link protocol that specifies the physical and media-acceas control layers over a broadband communication network. A variety of traffic types can be time division multiplexed and modulated for integrated transport within the single radio frequency channel. Thecae traffic types may include variable length data units and constant bit rate voice data units.
Although the present invention is particularly well suited for broadband wireless access networks, and shall be so described with respect to this application, the present invention also applies to bi-directional hybrid fiber/coax networks, which are akin to broadband wireless access networks, in that the cable modems do not usually directly listen to each other, but instead depend on the headend for feedback.
Therefore, it is understood that the present invention may also function in the context of a "headend" and a "cable modem", where the base station may be replaced with a headend. and access stations may be replaced by cable modems.
Figures 1 through Ei, and the accompanying detailed description contained herein, are to be used as an illustrative example of a preferred embodirnent of the present invention.
Details of the structure may be varied substantially without departing from the spirit of the invention.
Fig. 1 illustrates an exemplary point-to-multipoint broadband wireless access (BWA) system connected to IP backbone network with whuch the present invention may be used.
The system supports the delivery of integrated data and voice services to business and residential customers providing the operators with the ability to provision differentiated :services such as "tall quality"
voice, "mission-critical" data, and low priority "best-efforr." data. The base st;~tion is the central element of the BWA network, providing integrated multi-service access by dynamically scheduling packet flow between access stations and backbone networks. The access stations are the suite of local wireless hardware and integrated software products deployed at customer premises, which provide physical interfaces to data and voice equipments.
The access stations may interface with the base station at several frequency bands.
Fig. 2 illustrates an exemplary frame structure of the downstream transmission of the upstream bandwidth allocation m.ap (MAP) for the next upstream frame in accordance with the present invention.
The bandwidth allocation map uses time units of "mini-slots" that represent the byte-time needed for transmission of a fixed number of bytes. This MAP is generated by the MAP
generator in the base station based on the architecture presented in Fig 5. Successive MAPS are generated each containing Information ,-Elements. Each Information Element determines source identifier, usage and duration of the time-slot where each time slot can be used for bandwidth request, data transmission or maintenance.
Fig. 3 illustrates an example of an overall interchange between the access station and the base station when the access station has data to transrr~it.
At time t,, the base station transmits a MAP whose effective period is between t3 and t9. Among others, there is a Request element starting at t5. This lets the access stations know the starting contention period during which they can transmit their request for bandwidth. As we can see, the MAP is sent ahead of time to compensate for various delays in the system (e.g. propagation delay and processing delay).
At time tz, the access station receives the MAP and scans it for request opportunities. If every access station starts transmitting request at t4, there will be a collision in all request periods. To avoid this, each access station calculates t6 as a random offset and starts request at that time. An access station determines that a collision occurred when the next MAP fails to include acknowledgment of the request.
Upon reception of this reduest at t~, the base station schedules it for service in the next MAP.
At t~, the base station transmits a MAP whose effective starting time is t9.
Within this MAP, a data grant for the access station will start at t"
At t8, the access station receives the MAP, detects the data grant in it and starts transmission of data at t,o. The access station transmits its data so that it will arrive at the base station at t".
The methodology for slot allocation of multiple voice packets in upstream is provided by an example in Fig. 4. Fig. 4 (a) illustrates the conventional approach to reserve bandwidth for voice packets. Bandwidth is reserved for the exact time where the voice packet is available. This approach results in a randomly distributed voice packets among other types of data and management packets.
The random use of the voice slots results in the free slots being of unpredictable and random size. This increases the probability of fragmentation of data packets and results in poor bandwidth utilization.
Fig. 4 (b) illustrad~s the new appro<tch where all the voice grants are grouped together. Management of the voice grants is done by a module separate from the MAP generator. The total size of the voice grant is still variable because new voice sessions may join, others may leave and some others may switch between voice and silence, but 'the starting point of the grant is always periodic. It is obvious that this results in larger free slots, and consequently the probability of having fragmented data reduces considerably. The size of the MAP being variable, the position and number of voice slots in a MAP is also unpredictable. As it is shown in Fig. 4, there may be MAPS with no voice slot and others with one or more voice slots. Every time the MAP generator creates a new M~~P, it keeps track of the time up to which the upstream is allocated (based on the; IEs inserted in t:he MAP). At the appropriate time for the voice grant to be inserted (every T seconds), it asks the voice manal;er for the number of voice grants necessary at that time and inserts it into the MAP' under creation. If the MAP generator has to transmit the MAP without all the voice grants, it will keep the remaining grants and puts them in the next MAP. One major point stays to be considered: Do we need to shift all the voice grants to have them allocated during the big voice grant? The answer is positive but only for the first grant of any voice session that has been created or is switching from silence to voice. The maximum delay introduced this way is not greater than the period of the big voice grant (being equal to the period of packet generation). This delay is unnoticeable by the user because it is the inter-packet delay ~~hange that is noticeable in interactive communication. Each time an access station starts transmission of voice packets, some delay is already introduced for the base station, due to the propagation delay in the upstream, to receive the request and assign bandwidth to it. This covers the above delay. As a consequen~:e any additional delay is not introduced in the system.
Fig. 5 illustrates a proposed architecture comprising of a MAP generator and a Voice manager. The MAP generator receives requests from different sources. Two types of requests are considered in the figure:
~ requests for data transmission: the access station should obtain the permission by requesting to transmit and t:he MAP generator grants the request based on predefined policies.
~ requests from the voice manager: the voice manager keeps track of all the existing voice sessions and the timin;; of each one. It providers the MAP generator the grants to be serviced, at the right time. The Mf~P generator is not responsible for the number of voice grants;
this is managed by the voice manager which is already configured as to how much of the bandwidth is reserved for voice Now we will presc;nt the simulation results based on our methodology and on conventional approach that describe the number of times a dat<r packet is fragmented, and the number of times fragmentation is needed per second for data packets in the upstream, both with respect to voice utilization when the total bandwidth is utilized only for voice and data traffic. These results were obtained based on the probability distribution of incoming MAC data packet size as specified in Table 1. Voice packets were considered to be of fixed size and utilize exactly one mini slot of 101 bytes. It is also to be mentioned that in the simulation an amount of physical overhead size considered due to preamble and guard time is 30 bytes, and a fragmentation overhead considered is 16 bytes.
MAC PacketData Bytes Number of mini-slotsProbability per of Size mini-slot: per packet data packet (b tes) -_ - occurrence 70 _ 1 (min,max*) 0.35 400 101 5 (min*) 0.45 8 (max**) 1500 101 16(min*) 0.20 28 (max**) * when all mini slots are granted consecutively, there is only once a physical overhead of preamble ~~nd guard time, andl there is none fragmentation overhead; then MACPacketSize + PhysicalOverheadSize Nur,~berOfMinislotsPer-Packet =
DataBytesPerMinislot ** when only one mini slot is granted at a time, there is a physical overhead of preamble and guard time, and a fragmentation overhead in each mini slot; then MACPacketSize NumberOfMinislotsPerPacket -~(DatczB~tesPerMinislot - PhysicalOverheadSize - FragmentationOverhead) Table 1 Fig 6 illustrates a comparison of the number of times fragmentation of data packets is needed per second in the upstream for the conventional and proposed approaches. It is seen that in the conventional approach the number of fragmentations per second increases initially as the percentage of total bandwidth used for voice increases, and decreases as the total bandwidth is eventually utilized mainly for voice traffic and less and less is utilized for data traffic:. For different distribution of data packet size the shape will be the same but the maximum will be different. For example if the probability of larger size data packets is higher, the maximum number of fragment:ations per second will be high and the curve will move higher.
Similarly, in the case of probability of smaller size data packets is high in the distribution, the maximum number of fragmentations per second will be lower and the curve will move lower. The big advantage of the proposed inventive; approach is that the number of fragmentations per second is constant (except when there is no voice traffic and when there are no data packets, in which case there are no fragmentations) and it does not depend on the percentage of bandwidth utilized for voice. This number is related to the voice slot period as 1/T.
i
MIT~VIIZE FRAGMENTATION OF DATA PACKETS IN A BROADBAND
WIRELESS ACCESS SYSTEM THAT PROVIDES VOICE, DATA AND
MULTIMEDIA SERVICES
FIELD OF THE INVENTION
The present invention relates generally t.o the media access control protocol applied to a bi-directional communications medium, such as a Broadband Wireless Access system where competing access stations are connected via a bro;~dband wireless network to a common base station, to communicate different types of information, or traffic, such as voice, data, or control information. This invention also relates to bi-directional hybrid fibencoax networks, which are akin to broadband wireless access networks in offering a wide range of telecommunication services to residences and businesses.
BACKGROUND OF THE INVENTION
Currently a great deal of activity is directed towards broadband wireless access networks to connect multiple residential and business users using wireless systems in order to provide new interactive multimedia services, including telephony and data networking. The present invention is related to establish an upstream MAC (Me~3ia Access Control] protocol in the controller of the base station such that bandwidth is dynamically allocated for a mix of interactive and non-interactive traffic types. The conventional LAN protocols, for example CSMA/CD and R-ALOHA protocols, are not suitable for use in wireless systems because the wireless networks have separate upstream and downstream channels, and the subscribers can only listen to the downstream from the base station and transmit in the allocated upstream.
The subscribers cannot listen directly tca the upstream transmissions from other subscribers, and are therefore incapable of coordinating their' transmissions by themselves. Usage of the upstream is centrally managed in the base station.
Many media access protocols have been proposed. The Data-Over-Cable Service Interface Specification (DOCSI~~) standard has been initially developed by CATV
operators and CableLabs. This specification has begun. to find a home outside the TV market. Specifically, a group of companies formed a consortium, called the Wireless DSL Consortium, to produce an enhanced version of the standard for broadband wireless applications, and are currently under study by the IEEE
802.16 committee.
The upstream channel is modeled as a stream of mini-slots. Protocols have been proposed to describe the elements of requesting, granting, and using the upstream bandwidth. The basic mechanism for assigning bandwidth is the bandwidth allocation MAl' which describes the uses to which the upstream mini-slots must be put, and through which the base station controls access to these slots by the access stations. Many numbers of contiguous. slots may be granted to an access station to transmit data. A larger MAC PDU may need to be fragmented into smaller pieces that are individually transmitted and then reassembled at the base station.
The main objective of this inventic7n is to provide an optimum method of bandwidth allocation in a transmission system, and in particular in a. broadband wireless access network, such that the fragmentation of data packets is minimized to improve system performance while not introducing an additional delay and fitter into the real-time traffic.
SUMMARY OF THE INVENTION
Although there arc: protocols available that provide mechanisms for bandwidth allocation for multimedia traffic types, we propose another way to optimize the efficiency of bandwidth allocation in an access protocol that also minimizes the need for the fragmentation of larger data packets. In particular, and in accordance with achieving the objective of the present invention, a base station communicates to access stations via a broadband wireless access network using a media access control protocol, which is modified to support a variable number of voice mini-slots and a variable number of data mini-slots in each frame.
The base station dynamically adjusts the positioning of mini-slots over a period time for on-line voice traffic in order to reduce its random distribution and random availability of free mini-slots to be used for other traffic types. As a result, the inventive; concept allows the base station to efficiently utilize remaining bandwidth on the communications channel for data traffic by minimizing their fragmentation. It should be noted that the fragmentation introduces overhead by adding extra fragmentation header, and costs more memory and CPU cycles for the packet assembly and disassembly functions. For example, the number of times all larger data packets are fragmented will introduce a bandwidth overhead at least equal to the product of this number and the fragmentation overhead. The objective of the present invention is to minimize the addition of this fragmentation overhead by minimizing the need for fragmentation.
In an embodiment of the invention, a base station communicates to access stations via a broadband wireless access network using the conventional DOCSIS based media access control protocol, which is modified to dynamically allocate bandwidth such that the on-line voice traffic mini-slots are positioned back-to-back and the remaining mini-slots. can service larger data packets without fragmentation. Any presence of voice silence reflects in its mini-slat being dynamically utilized for other traffic types and affects the size of contiguous data slots available to service best effort traffic. For example, less voice slots provide larger data slots to service larger data traffic.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 illustrates an exemplary arrangement of a broadband wireless access network utilized in accordance with the present invention, the network connecting a base station to a plurality of access stations for downstream signal broadcasting and allowing upstream information transmission from the individual access statians to the base station as well;
--2_ DETAILED DESCRIPTION OF THE INVENTION
The present invention encompasses a system utilizing a broadband link protocol that specifies the physical and media-acceas control layers over a broadband communication network. A variety of traffic types can be time division multiplexed and modulated for integrated transport within the single radio frequency channel. Thecae traffic types may include variable length data units and constant bit rate voice data units.
Although the present invention is particularly well suited for broadband wireless access networks, and shall be so described with respect to this application, the present invention also applies to bi-directional hybrid fiber/coax networks, which are akin to broadband wireless access networks, in that the cable modems do not usually directly listen to each other, but instead depend on the headend for feedback.
Therefore, it is understood that the present invention may also function in the context of a "headend" and a "cable modem", where the base station may be replaced with a headend. and access stations may be replaced by cable modems.
Figures 1 through Ei, and the accompanying detailed description contained herein, are to be used as an illustrative example of a preferred embodirnent of the present invention.
Details of the structure may be varied substantially without departing from the spirit of the invention.
Fig. 1 illustrates an exemplary point-to-multipoint broadband wireless access (BWA) system connected to IP backbone network with whuch the present invention may be used.
The system supports the delivery of integrated data and voice services to business and residential customers providing the operators with the ability to provision differentiated :services such as "tall quality"
voice, "mission-critical" data, and low priority "best-efforr." data. The base st;~tion is the central element of the BWA network, providing integrated multi-service access by dynamically scheduling packet flow between access stations and backbone networks. The access stations are the suite of local wireless hardware and integrated software products deployed at customer premises, which provide physical interfaces to data and voice equipments.
The access stations may interface with the base station at several frequency bands.
Fig. 2 illustrates an exemplary frame structure of the downstream transmission of the upstream bandwidth allocation m.ap (MAP) for the next upstream frame in accordance with the present invention.
The bandwidth allocation map uses time units of "mini-slots" that represent the byte-time needed for transmission of a fixed number of bytes. This MAP is generated by the MAP
generator in the base station based on the architecture presented in Fig 5. Successive MAPS are generated each containing Information ,-Elements. Each Information Element determines source identifier, usage and duration of the time-slot where each time slot can be used for bandwidth request, data transmission or maintenance.
Fig. 3 illustrates an example of an overall interchange between the access station and the base station when the access station has data to transrr~it.
At time t,, the base station transmits a MAP whose effective period is between t3 and t9. Among others, there is a Request element starting at t5. This lets the access stations know the starting contention period during which they can transmit their request for bandwidth. As we can see, the MAP is sent ahead of time to compensate for various delays in the system (e.g. propagation delay and processing delay).
At time tz, the access station receives the MAP and scans it for request opportunities. If every access station starts transmitting request at t4, there will be a collision in all request periods. To avoid this, each access station calculates t6 as a random offset and starts request at that time. An access station determines that a collision occurred when the next MAP fails to include acknowledgment of the request.
Upon reception of this reduest at t~, the base station schedules it for service in the next MAP.
At t~, the base station transmits a MAP whose effective starting time is t9.
Within this MAP, a data grant for the access station will start at t"
At t8, the access station receives the MAP, detects the data grant in it and starts transmission of data at t,o. The access station transmits its data so that it will arrive at the base station at t".
The methodology for slot allocation of multiple voice packets in upstream is provided by an example in Fig. 4. Fig. 4 (a) illustrates the conventional approach to reserve bandwidth for voice packets. Bandwidth is reserved for the exact time where the voice packet is available. This approach results in a randomly distributed voice packets among other types of data and management packets.
The random use of the voice slots results in the free slots being of unpredictable and random size. This increases the probability of fragmentation of data packets and results in poor bandwidth utilization.
Fig. 4 (b) illustrad~s the new appro<tch where all the voice grants are grouped together. Management of the voice grants is done by a module separate from the MAP generator. The total size of the voice grant is still variable because new voice sessions may join, others may leave and some others may switch between voice and silence, but 'the starting point of the grant is always periodic. It is obvious that this results in larger free slots, and consequently the probability of having fragmented data reduces considerably. The size of the MAP being variable, the position and number of voice slots in a MAP is also unpredictable. As it is shown in Fig. 4, there may be MAPS with no voice slot and others with one or more voice slots. Every time the MAP generator creates a new M~~P, it keeps track of the time up to which the upstream is allocated (based on the; IEs inserted in t:he MAP). At the appropriate time for the voice grant to be inserted (every T seconds), it asks the voice manal;er for the number of voice grants necessary at that time and inserts it into the MAP' under creation. If the MAP generator has to transmit the MAP without all the voice grants, it will keep the remaining grants and puts them in the next MAP. One major point stays to be considered: Do we need to shift all the voice grants to have them allocated during the big voice grant? The answer is positive but only for the first grant of any voice session that has been created or is switching from silence to voice. The maximum delay introduced this way is not greater than the period of the big voice grant (being equal to the period of packet generation). This delay is unnoticeable by the user because it is the inter-packet delay ~~hange that is noticeable in interactive communication. Each time an access station starts transmission of voice packets, some delay is already introduced for the base station, due to the propagation delay in the upstream, to receive the request and assign bandwidth to it. This covers the above delay. As a consequen~:e any additional delay is not introduced in the system.
Fig. 5 illustrates a proposed architecture comprising of a MAP generator and a Voice manager. The MAP generator receives requests from different sources. Two types of requests are considered in the figure:
~ requests for data transmission: the access station should obtain the permission by requesting to transmit and t:he MAP generator grants the request based on predefined policies.
~ requests from the voice manager: the voice manager keeps track of all the existing voice sessions and the timin;; of each one. It providers the MAP generator the grants to be serviced, at the right time. The Mf~P generator is not responsible for the number of voice grants;
this is managed by the voice manager which is already configured as to how much of the bandwidth is reserved for voice Now we will presc;nt the simulation results based on our methodology and on conventional approach that describe the number of times a dat<r packet is fragmented, and the number of times fragmentation is needed per second for data packets in the upstream, both with respect to voice utilization when the total bandwidth is utilized only for voice and data traffic. These results were obtained based on the probability distribution of incoming MAC data packet size as specified in Table 1. Voice packets were considered to be of fixed size and utilize exactly one mini slot of 101 bytes. It is also to be mentioned that in the simulation an amount of physical overhead size considered due to preamble and guard time is 30 bytes, and a fragmentation overhead considered is 16 bytes.
MAC PacketData Bytes Number of mini-slotsProbability per of Size mini-slot: per packet data packet (b tes) -_ - occurrence 70 _ 1 (min,max*) 0.35 400 101 5 (min*) 0.45 8 (max**) 1500 101 16(min*) 0.20 28 (max**) * when all mini slots are granted consecutively, there is only once a physical overhead of preamble ~~nd guard time, andl there is none fragmentation overhead; then MACPacketSize + PhysicalOverheadSize Nur,~berOfMinislotsPer-Packet =
DataBytesPerMinislot ** when only one mini slot is granted at a time, there is a physical overhead of preamble and guard time, and a fragmentation overhead in each mini slot; then MACPacketSize NumberOfMinislotsPerPacket -~(DatczB~tesPerMinislot - PhysicalOverheadSize - FragmentationOverhead) Table 1 Fig 6 illustrates a comparison of the number of times fragmentation of data packets is needed per second in the upstream for the conventional and proposed approaches. It is seen that in the conventional approach the number of fragmentations per second increases initially as the percentage of total bandwidth used for voice increases, and decreases as the total bandwidth is eventually utilized mainly for voice traffic and less and less is utilized for data traffic:. For different distribution of data packet size the shape will be the same but the maximum will be different. For example if the probability of larger size data packets is higher, the maximum number of fragment:ations per second will be high and the curve will move higher.
Similarly, in the case of probability of smaller size data packets is high in the distribution, the maximum number of fragmentations per second will be lower and the curve will move lower. The big advantage of the proposed inventive; approach is that the number of fragmentations per second is constant (except when there is no voice traffic and when there are no data packets, in which case there are no fragmentations) and it does not depend on the percentage of bandwidth utilized for voice. This number is related to the voice slot period as 1/T.
i
Claims (8)
1. A method for use in the transport of different types of traffic via an access protocol in a system of broadband wireless access, the access protocol defining a bandwidth allocation map that includes a plurality of mini time slots for transporting the different types of information, said method comprising the steps of:
dividing said transmission into a series of successive time frames;
dividing each of said time frames into first and second regions leaving no unassigned bandwidth in between where first region is at the beginning of the frame, and each of said first and second regions containing zero or more mini slots;
said first region consisting of zero or more voice slots each comprising of a fixed length time mini slot, and said second region consisting of zero or more variable length data slots each comprising of a number of fixed length time mini slots;
dynamically varying the position of voice slots in each frame such that voice slots corresponding to all active voice sessions are placed in the first region, and thereby increasing the number of contiguously available data slots to be placed in the second region.
dividing said transmission into a series of successive time frames;
dividing each of said time frames into first and second regions leaving no unassigned bandwidth in between where first region is at the beginning of the frame, and each of said first and second regions containing zero or more mini slots;
said first region consisting of zero or more voice slots each comprising of a fixed length time mini slot, and said second region consisting of zero or more variable length data slots each comprising of a number of fixed length time mini slots;
dynamically varying the position of voice slots in each frame such that voice slots corresponding to all active voice sessions are placed in the first region, and thereby increasing the number of contiguously available data slots to be placed in the second region.
2. A method for use in the transport of different types of traffic via an access protocol in a system of broadband wireless access, the access protocol defining a bandwidth allocation map that includes a plurality of mini time slots for transporting the different types of information; whereby the number of the voice slots depend on the number of voice sessions and also on the number of them that are active (so need grant for voice packet) and the number that are in the polling mode for traffic generated on a periodic basis (so need grant for polling packet).
3. A method for use in the transport of different types of traffic via an access protocol in a system of broadband wireless access, the access protocol defining a bandwidth allocation map that includes a plurality of mini time slots for transporting the different types of information; the said method comprising the steps of claim 1 wherein said dynamic positioning provides a reduction in the complicated process of fragmentation of data traffic.
4. A method for use in the transport of different types of traffic via an access protocol in a system of broadband wireless access, the access protocol defining a bandwidth allocation map that includes a plurality of mini time slots for transporting the different types of information; the said method comprising claim 1, claim 2 and claim 3 provides an improvement in the bandwidth utilization.
5. The method according to claim 1, as applied to unsolicited grant services that may become inactive for substantial amount of time, such as Voice over IP with silence suppression, reduces the total number of voice slots in first region thereby increasing number of available data mini-slots in second region minimizing their fragmentation.
6. The method according to claim 1 allows for new voice sessions to join and the old ones to leave without degrading bandwidth utilization.
7. An apparatus for use in the transport of different types of traffic via an access protocol in a system of broadband wireless access, wherein voice traffic for active sessions, for real-time polling sessions, for new voice sessions, and for leaving sessions are managed to provide the number of voice grants necessary to be inserted into the MAP under creation
8. A method for use in the transport of different types of traffic via an access protocol in a system of broadband wireless access, the access protocol defining a bandwidth allocation map that includes a plurality of mini time slots for transporting the different types of information; the said method utilizes, if needed, a fixed number of times fragmentation of the data traffic in the upstream per second, which is in contrast to the conventional approach where the number of times fragmentation of the data traffic needed is proportional to the number of voice sessions.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002349115A CA2349115A1 (en) | 2001-05-25 | 2001-05-25 | Method and apparatus for dynamic bandwidth allocation to minimize fragmentation of data packets in a broadband wireless access system that provides voice, data and multimedia services |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002349115A CA2349115A1 (en) | 2001-05-25 | 2001-05-25 | Method and apparatus for dynamic bandwidth allocation to minimize fragmentation of data packets in a broadband wireless access system that provides voice, data and multimedia services |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2349115A1 true CA2349115A1 (en) | 2002-11-25 |
Family
ID=4169155
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002349115A Abandoned CA2349115A1 (en) | 2001-05-25 | 2001-05-25 | Method and apparatus for dynamic bandwidth allocation to minimize fragmentation of data packets in a broadband wireless access system that provides voice, data and multimedia services |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2349115A1 (en) |
-
2001
- 2001-05-25 CA CA002349115A patent/CA2349115A1/en not_active Abandoned
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