Quality Of Service In Wimax And Lte Networks 6ia18

Quality of Service in WiMAX and LTE Networks Mehdi Alasti and Behnam Neekzad, Clearwire Jie Hui and Rath Vannithamby, Intel Labs IEEE Communications Magazine • May 2010 報告者：李宗穎

Outline   

 

Introduction QoS in IEEE 802.16e QoS in IEEE 802.16m QoS in Long Term Evolution (LTE) Comparison and Conclusions

2

Introduction 

4G broadband wireless technologies such as IEEE 802.16e, IEEE 802.16m, and 3GPP LTE have been designed with different QoS frameworks 

Guarantee different traffic patterns and distinct QoS requirements

3

QoS in IEEE 802.16e The QoS framework in IEEE 802.16e is based on service flows

Service Flow

4

802.16e Service Flow Management 802.16e MS

802.16e BS

 

DSA_REQ



Dynamic Service Change (DSC) Dynamic Service Delete (DSD) Dynamic Service Activate (DSA)

DSX_RVD

DSD

DSC DSA_RSP

DSA_ACK

NULL

DSA OPERATIONAL

5

802.16e Service Flow ID (SFID) Name

SIZE

I

Uplink/Downlink

1

S

Maximum sustained traffic rate

6

T

Traffic indication preference (Sleeping mode)

1

B

Maximum traffic burst

6

R

Minimum reserved traffic rate

6

L

Maximum latency

6

S

Fixed-length VS variable length SDU indicator

1

P

Paging preference (Idle mode)

1

R

Reserved

4 6

Service Flow Types in IEEE 802.16 

Unsolicited grant service (UGS) 



Real-time polling service (rtPS) 



s real-time traffic with variable-size data packets on a periodic basis

Non-real-time polling service (nrtPS) 



s real-time traffic with fixed-size data packets on a periodic basis

s delay-tolerant traffic that requires a minimum reserved rate

Best effort (BE) service 

s regular data services 7

IEEE 802.16 Bandwidth Request (BR) and Grant Mechanism 

Contention-based (nrtPS、BE)  



BS allocates bandwidth for the BR message MS uses a code-division multiple access (CDMA)-based mechanism

Contention free-based (rtPS、nrtPS)  



piggybacked bandwidth request BS polls MS periodically set poll me (PM) bit in the header of a UGS 8

Request/Grant for ertPS (802.16e) 

using by VoIP with silence suppression 

during a talk spurt 





BS provides unicast grants in an unsolicited manner as in UGS An MS uses its periodic allocation for both data transfer and bandwidth request adjustments

during a silence period 



the allocation is taken from the ertPS SF the MS sends a BR message to the BS with a silence-to-talk-spurt transition 9

IEEE 802.16m QoS Framework 

IEEE 802.16m advanced air interface (AAI), provides a more flexible and efficient QoS framework    

adaptive granting and polling (aGP) service quick access delayed BR and priority controlled access 10

adaptive granting and polling (aGP) service 

UGS, ertPS, and rtPS are not efficient for applications such as online games, VoIP with adaptive multi-rate (AMR), and delaysensitive T based services 

more flexible QoS scheduling service to the adaptation of both the allocation size and inter-arrival

11

the new QoS parameters in the aGP service 

primary grant polling interval (GPI) and primary grant size; and optional ones: secondary GPI, secondary grant size, and adaptation method 



Advanced BS (ABS) grant advanced MS (AMS) UL allocation GPI with grant size ABS poll AMS for BR periodically every GPI

12

aGP mechanism 

During a service, the traffic characteristics and QoS requirements may change 

adaptation of scheduling state includes switching between using primary and secondary SF QoS parameters or changing the GPI and/or grant size

13

mix of IEEE 802.16m and legacy IEEE 802.16e 

AMS handover from an IEEE 802.16m network to an IEEE 802.16e network 



If primary grant size value is equal to the BR header size, it means this aGP SF is primarily polling-based SF, and hence should be mapped to an rtPS SF Otherwise, this aGP SF is primarily a granting based service, and thus should be mapped to an ertPS SF 14

Quick Access 

the BR message is communicated from MS to BS only after random access is successful 





Random access delay is a significant part of UL access delay Quick access in IEEE 802.16m helps reduce the random access delay

Quick Access Message 

12-bit station ID and 4-bit predefined BR index 15

Contention-based Random Access BW-REQ 5-step contention-based BW-REQ

3-step contention-based BW-REQ

16

Delayed BR for BE 



The service-specific BR header specifies a minimum grant delay to indicate the minimum delay of the requested grant for BE scheduling service When an AMS is cleaning out its buffers, in one UL transmission it can send a delayed BR asking for future packet(s) with minimum expected grant delay if AMS can predict the future packet(s) arrival time 17

Priority Controlled Access 



An operator can assign AMS with different access classes and block random access from certain AMSs by asg a minimum access class of the network higher than the access class of those AMSs The BR timer and random backoff parameters can also use different values to differentiated random access in IEEE 802.16m 18

LTE QoS Framework 



The traffic running between a particular client application and a service can be differentiated into separate service data flows (SDFs) SDFs mapped to the same bearer receive a common QoS treatment

19

LTE bearer 

A bearer is assigned a scalar value referred to as a QoS class identifier (QCI)  

Guaranteed bit rate (GBR) Non-guaranteed bit rate (non-GBR) 

A non-GBR bearer is referred to as the default bearer, which is also used to establish IP connectivity, similar to the initial SF in WiMAX

20

QoS attributes associated with the LTE bearer 

QoS class identifier (QCI) 



Allocation and retention priority (ARP) 

  

A scalar representing a set of packet forwarding treatments A parameter used by call ission control and overload control

Maximum bit rate (MBR) Guaranteed bit rate (GBE) Aggregate MBR (AMBR) 

The total amount of bit rate of a group of non-GBR bearers 21

LTE standardized QCI characteristics

22

LTE Air Interface Scheduler 

the LTE air interface scheduler uses the following information as input   

Radio conditions at the UE identified The QoS attributes of bearers The interference situation in the neighboring cells

23

Buffer Status Reporting 

The buffer status reporting mechanism informs the UL packet scheduler about the amount of buffered data at the UE 



A periodic BSR trigger does not cause a service request (SR) transmission from the UE Otherwise, the SR is transmitted via a random access procedure 



Short format can be used to report on one radio bearer group Long format one can be used for four groups

24

802.16 and LTE comparison (1/3) 

QoS transport unit  



IEEE 802.16  service flow between MS and BS LTE  bearer between UE and the PDNGW

QoS scheduling types 



IEEE 802.16  UGS, ertPS, rtPS, nrtPS, BE, and aGP service LTE  GBR mechanism is like rtPS; non-GBR mechanism is like BE 25

802.16 and LTE comparison (2/3) 

QoS parameters per transport unit 



LTE MBR and GBR are similar to IEEE 802.16 maximum sustained traffic rate and minimum reserved traffic rate LTE AMBR allows the operator to rate cap the total non-GBR bearers of a subscriber

26

802.16 and LTE comparison (3/3) 

QoS handling in the control plane 



The SF QoS parameters are signaled in IEEE 802.16 via DSx/AAI-DSx messages In LTE the QCI and associated nine standardized characteristics are not signaled on any interface

27

Conclusion 



Fourth-generation wireless technologies such as IEEE 802.16e, IEEE 802.16m, and LTE are designed to current and future QoS needs This article explains the QoS framework of IEEE 802.16e, IEEE 802.16m, and LTE, and compares their QoS features against each other 28