ABSTRACT
Contents 9.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 298
9.1.1 Iub/Iur Transport Network Architecture . . . . . . . . . . . . . . . . . . . . 298 9.1.2 Requirements, Different Traffic Types . . . . . . . . . . . . . . . . . . . . . . 304 9.1.3 Transport Network Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 305
9.1.3.1 Typical Capacities and Architecture . . . . . . . . . . . . . . . 306 9.2 Congestion Avoidance Mechanisms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 306
9.2.1 Buffering and QoS Differentiation . . . . . . . . . . . . . . . . . . . . . . . . . . 307 9.2.2 Flow-Level Congestion Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 308 9.2.3 Call Admission Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 308 9.2.4 Link Dimensioning. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 309 9.2.5 Congestion Avoidance Example. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 309
9.3 HSPA Flow Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 310 9.3.1 Congestion Detection and Network Monitoring . . . . . . . . . . . . 312 9.3.2 Congestion Action . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 314 9.3.3 Per-Flow HSPA Flow Control Solutions . . . . . . . . . . . . . . . . . . . . . 316 9.3.4 Aggregated HSPA Flow Control Solutions . . . . . . . . . . . . . . . . . . 316 9.3.5 Case Study: Aggregated HSDPA Flow Control Solution . . . . 317
9.3.5.1 Node B-Level Aggregation . . . . . . . . . . . . . . . . . . . . . . . . . 318 9.3.5.2 Uu Rate Estimation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 318
9.3.6 Case Study: Per-Flow HSUPA Flow Control Solution . . . . . . . 319 9.3.6.1 Transport Network Congestion Detection . . . . . . . . . 319 9.3.6.2 Bit Rate Calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 319
9.3.6.3 Congestion Action in the Serving Cell . . . . . . . . . . . . . 320 9.3.6.4 Congestion Action in the Non-Serving Cell . . . . . . . 320
9.3.7 Other Flow Control Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 320 9.4 HSPA Framing Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 321 9.5 TNL Overhead . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 326 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 329
9.1 Introduction The introduction of High-Speed Packet Access (HSPA) greatly improves the achievable bit rate but it presents new challenges to be solved in the Wideband Code Division Multiple Access (WCDMA) radio access network (RAN). For dedicated channels (DCHs), transport network bandwidth can be reserved by means of admission control. Bandwidth reservation is not efficient for HSDPA because of the higher peak rates and much higher variance of achieved bit rate; thus a new solution is needed to control congestion. In the Internet, such congestion is controlled by the end-user Transmission Control Protocol (TCP), but that is not possible in the access transport network because lost packets are retransmitted by WCDMA-specific lower layers.
