CEPT ECC Electronic Communications Committee Asymmetrical Links in Packet-based Mobile Transport Networks Ian Sutton, Anders Vahlin, Rami Lerner March, 2012
Agenda Asymmetrical links concept and benefits Review a real life network example Summary 2
Legacy Communication Systems Voice Oriented Networks Downstream Tail site Upstream Symmetric channel within FDD frequency plan Aggregation/ Hub site Aggregation Network TDM Voice traffic dominates DL and UL bandwidth allocation is equal Wireless P2P links are based on voice paradigms (SDH/PDH) Regulators provide the same amount of spectrum in both directions 3
Modern Communications Asymmetrical by Nature Modern communication is asymmetrical by nature Browsing Video streaming The Base station - Handheld channel will always be asymmetrical ~10dB difference, BTS to handset TX power half the capacity in the uplink. Capacity increasing techniques on the UL (MIMO, Channel aggregation) requires TX amplifiers addition Quickly draining the handheld battery Not practical. Cloud computing: May cause more UL capacity storing work on the web But, will also cause more DL capacity Downloading this info to several devices. Many of the cloud computing applications are DL oriented sending only the differences on the UL. 4
Benefits of Asymmetrical Spectrum Usage Tuned to the needs of 3G/4G networks Downstream Tail site Upstream Asymmetrical channel within FDD frequency plan Aggregation/ Hub site Aggregation Network Dramatically increase backhaul spectrum utilization Less spectrum for services - avoid spectrum congestion More capacity-per-site using same spectrum allocation Support more links in a given geographical area Increase spectrum channel reuse Better Operator TCO - promotes services growth for public benefit 5
DL:UL Ratio Asymmetrical Links Test Case Real Life Network Analysis DL:UL Ratio 79 40 25 16 10 6 4 3 2 1 0 200 400 600 800 1000 1200 1400 1600 Number of Links Large mobile operator in western Europe Study encompassing 5415 links Entire network; access and aggregation 96% with DL:UL ratio higher than 2:1 6
Utilization % Asymmetrical Links Test Case Real Life Network Analysis - Utilization Number of Links 0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 0-10% 956 10-20% 20-30% 1385 1395 30-40% 999 40-50% 430 50-60% 184 60-70% 70-80% 80-90% 90-100% 42 12 8 4 99% of the links, with less than 80% utilization Combined with the previous picture we understand why 7
Benefits of Asymmetrical Spectrum Usage Theoretical Example 1: Chain1 Chain1 5 6 7 8 3 4 5 6 5 6 7 8 25% less spectrum 5 6 Agg.1 Agg.1 1 2 3 4 1 2 3 4 1 2 3 4 1 2 Tail 1 Tail 2 Tail 1 Tail 2 Assuming you can t reuse the frequencies Saving 25% of spectral resources 8
Benefits of Asymmetrical Spectrum Usage Theoretical Example 2: Chain1 Chain1 5 6 7 8 3 4 5 6 7 8 5 6 7 8 50% more capacity 7 8 Agg.1 Agg.1 1 2 3 4 1 2 3 4 5 6 1 2 3 4 1 2 Tail 1 Tail 2 Tail 1 Tail 2 Assuming you can t reuse the frequencies Getting 50% more capacity 9
Benefits of Asymmetrical Spectrum Usage Real life Example (XPIC links) 3: PoP PoP Site D Site D Site A 1W4L 1W4H Site A Site E 5W6L 5W6H 7W8L 7W8H HuB 7W8H 7W8L 5W6H 5W6L Site B Site E 5L V 5W6H 6L V 1W2H 1W4L V 3W4H HuB 1W2H V 6L 5W6H V 5L Site B 5W6L 5W6H 5L V 5W6H Site C Site C Adding sites D and E requires additional channels - 7,8 Adding sites D and E reusing channels 1,2 from the aggregation link. 10
Technology is Available for All Radio Technology MODEMs can be SW configured to control system spectral utilization. All MW vendors are already doing so - ACM. Planning Tools Same process as for symmetrical link planning. Propagation Symmetrical and Asymmetrical links behave the same. Planning SW Asymmetrical planning requires different parameters within the same inputs framework (C/I, NFD ). Frequency coordination Already performing bi-directional links coordination (Both stations independently assessed in terms of interference causing and generating) Asymmetrical Links NOT a Paradigm Change 11
Summary Asymmetrical planning shows definite spectrum saving In any scenario. Another tool in the planning tool box not a mandatory requirement. Based on available standardisation, channel plans and working process Not a paradigm change! Ceragon recommends: Adopting unidirectional allocation of spectrum for P-P links. Allowing concatenation of Nx7MHz channels 12