Scheduling in Wireless Systems

2 CDMA2000: Overall Architecture Mobile Station

3 Reference Points (Interfaces) TE2 MT2 RAN Rm Um Mobile Station TE2 : Terminating Equipment 2 MT2 : Mobile Terminal 2 RAN : Radio Access Network Connectivity to the network External device (Laptop) Data processing device Phone service (voice) InterfaceEntitiesApplicable standard RmTE2 – MT2IS-707 UmRAN - MSIS-2000/IS-707

4 Radio Access Network (RAN) MS A7 Base Station BSC BTS A bis PCFPDSN MSC Base Station BSC BTS A bis Um Signaling A3 User Traffic, Signaling A9 A8 Signaling User Traffic A1 (Signaling) A2 (Voice) A5 (CS data traffic) A11 A10 Signaling User Traffic BSC : Base Station Controller BTS : Base Transceiver Station PCF : Packet Control Function PDSN : Packet Data Serving Node MSC : Mobile Switching Center CS : Circuit-Switched

5 Base Transceiver Station (BTS) Terminating the radio links with the mobile station RF resources such as frequency assignments, sector separation, transmit power control BTS connects to BSC through un-channelized T1 facilities or direct cables in co-located equipment (A bis ) –The protocols are proprietary and are based on High-level data link control (HDLC) Typically terminates the IS-2000 LAC/MAC protocols for common channels, although in some implementations such protocols are terminated at the BSC In case of dedicated channels, the BTS exchanges physical layer frames with the BSC over A bis interface Typically equated to the physical site of the wireless network where antennas are located 3-cell BTS configuration is most common (max. up to 6 cell BTS)

6 Base Station Controller (BSC) Call processing Radio resource management Mobility management Transmission facilities management SDU (Selection/distribution unit) : when soft handoff, this selects the best incoming air interface data frame from the receivers Vocoder BSC-BTS : A bis  a set of trunks : backhaul BSC-MSC : A1/A2/A5  a set of trunks : fronthaul

7 Packet Control Function (PCF) Maintains the status of the radio resources associated with a packet data call  bursty traffic Main functionality is to direct PPP connection requests from TE to the appropriate PDSN that should handle the TE (or from BS to PDSN) Control between active period and inactive period Can be a standalone device serving multiple BSCs, or it can be implemented within one BSC

8 CDMA 1xEv-DO Evolution of CDMA2000 3G Data only Some radio resource management (RRM) functions moved from BSC to BTS –Packet scheduling in BTS –AMC –HARQ Downlink data rate –2.4Mbps in Rev. 0 –3.1Mbps in Rev. A –4.9Mbps in Rev. B Single user per time slot –No power control –Rate control important Slot size 1.67ms

9 Scheduling algorithms Round robin Max C/I Proportional Fair –Moving average of throughput –User selected Policy-based QoS-aware Scheduling

10 Example: Policy Rules Gold and Silver Classes –Gold user’s min. throughput: 128kbps –Silver user’s min. throughput: 64kbps Rule 1 –All gold users have higher priority and should achieve 128kbps. Rule 2 –Silver users should have higher priority than any gold user whose throughput is higher than 128kbps. Rule 3 –Once all gold and silver users have received their minimum throughput, the remaining should be distributed such that the ratio of the th(gold)/th(silver)=2.

11 BTS Function Architecture

12 Marginal Utility Function

13 Fixed MSs

14 Overloaded

15 Mobility

16 Fairness