New Network Architecture Digivance ® Simulcast Networks Reduce Network Costs and Improve Quality of Service WHITE PAPER Improving Grade of Service (GOS) While Reducing RF Channels Wireless service providers are adopting new deployment strategies to reduce network costs and improve quality of service. In one urban market, a major national wireless service provider has improved network traffic loading and significantly boosted network RF performance by centralizing radio equipment and deploying digital RF transport technology. The digital RF transport systems operate in simulcast mode and reproduce the signal at radiating points throughout the network. The new network architecture has produced trunking and channel re-use performance gains that enable the service provider to deliver greater GOS while reducing the number of RF channels. To achieve greater capacity with fewer RF channels, network designers used two or more ADC Digivance digital RF transport systems operating in “simulcast” mode at radiating points throughout the network. This white paper describes that simulcast network architecture, network traffic loading improvements and how the team determined the number of RF channels needed to achieve the desired GOS. Digivance ® Simulcast Networks Reduce Network Costs and Improve Quality of Service New Network Architecture New Network Architecture Page 3 What is "Simulcast"? A wireless simulcast communications system is defined as a signal (or group of signals) that is transmitted from a central transceiver and identically reproduced to several radiating points, with all received signals from these radiating points sent for recovery at the central transceiver’s receive circuitry. In the case of Digivance technology, the “central transceiver” is the Base Transceiver System (BTS)/Digivance host location, and the “several radiating points” are multiple Digivance remote units, as shown in this example of a Long-Range Coverage Solution (LRCS) simulcast deployment diagram: ADC’s patented Digivance digital RF spectrum transport solution is uniquely suited as the infrastructure of a simulcast network due to the inherent qualities of a digital fiber system. These benefits include: • Highest optical budget in the transport industry • Exceptional RF performance throughout entire optical budget • Lowest reverse path cascaded noise figure in the transport industry • Present WDM and CWDM optic capability, with future DWDM capability How Does a Digivance Simulcast System Create a Network Traffic Loading Improvement? The benefits of simulcast coverage in the service provider’s urban network are due to a reduction in the number of BTS sectors and an increase in channel loading per sector. This improves trunking efficiency (remember: calls cannot trunk between sectors). In the urban LRCS network, the new architecture reduced by 30 percent or more of the total number of RF channels required on a multiple link transport system for a specified amount of user grade of service. The percentage reduction depended on the number of radiating points and trunks required for the coverage area. In all communications systems that carry more than one user at a time, several communication links (i.e. voice “trunks”) must be provisioned to allow for all anticipated users to gain reasonable access to the network. What determines “reasonable access” is the designated “grade of service” (GOS), which is the acceptable amount of network blocking of incoming call attempts. Typical wireless network designs in the United States provision channels to provide voice services at a GOS of approximately 2 percent, with data services typically provisioned at a GOS of 4 to 5 percent. To determine the number of RF channels (voice trunks), the GOS and anticipated traffic intensity (Erlangs) must be known. Conversely, if you know the number of voice trunks available and the GOS, you can calculate traffic intensity supported. “Trunking efficiency” is simply the observation that the more voice trunks available - the less the chance of blocking, and is best explained by the Erlang B (non- queuing requests) formula: Where: B = Blocking% (GOS) A = Offered Traffic Load (Erlangs) N = Number of Available Trunks BTS Site Controller BTS Sector 1 Interface Panel FP 3:1 RP 3:1 Host 1 Host 2 Host 3 BTS Sector 1 Interface Panel FP 2:1 RP 2:1 Host 4 Host 5 Remote 1 Remote 2 Remote 3 Remote 4 Remote 5 A N N! B= i i! i=0 N A ∑ Core Urban Market - A “Real World” Case Study Here is an actual service provider’s market application of LRCS in two separate 2:1 simulcast configurations. In the original metro “RF hotel” configuration of five radiating points (a traditional BTS deployment of one radiating point per sector), the service provider operated five BTS sectors dedicated to five separate radiating points in strategic locations to obtain desired capacity and coverage in the metro core, as shown in diagram below: With average Radio Frequency channel (RFc) provisioning for this configuration of six RFcs (a maximum of 17 interconnect voice trunks) per sector, the acceptable offered interconnect load (GOS = <2%) was 10.6 Erlangs per sector. Given an interconnect traffic intensity total in Erlangs = (10.6E * (# of sectors)), any two sectors within this BTS would support 21.2 Erlangs at 2% GOS. After the five LRCS sectors were optimized and confirmed to be operating with excellent statistics, the urban market began to test the ADC recommended simulcast strategies. This is a diagram detailing the customer conversion to one sector of simulcast: By combining two of these radiating points into a single BTS sector and increasing the base radio count of that sector to 10RFcs (26-29 interconnect voice trunks maximum), trunking efficiencies are increased to 21.1 Erlangs at 2% GOS traffic support on a single simulcast sector. Capacity comparison: (21.1E)/(21.2E) = 0.995% Required Radio Frequency Channels: 10RFc(simulcast)/12RFc(RFc S 2 sectors) = 0.833% An initial conclusion can be drawn that this configuration allows for virtually identical capacity (at 0.995%) with 17 percent fewer BTS radio channels required… an impressive number in itself. There is also an opportunity for data services to realize the benefits of increased trunking efficiencies of a Digivance digital simulcast network. So for the direct connect and packet data services queuing calculation using Erlang C provisioning is: In this network deployment, the service provider realized significant cost savings and found that they could actually reduce to one sector with nine RFcs from two sectors averaging 13 RFcs (2 sectors of 6RFc + 7 RFc), a BTS radio reduction of 31percent. In addition, it was observed that low cost/low power 2:1 splitters and combiners could be used for forward and reverse paths to couple signals between a single interface and two host units. This reduced the amount of interface circuitry required in the network and produced another cost savings from the simulcast system. After realizing this savings (and being assured by continued excellent system performance statistics and RF measurements) the service provider repeated this 2:1 simulcast process again with the same results. New Network Architecture Page 4 BTS Site A Controller BTS Site B Controller Sector 1 (6RFc) Sector 2 (6RFc) Sector 3 (6RFc) Sector 4 (6RFc) Sector 5 (6RFc) BTS Interface BTS Interface BTS Interface BTS Interface BTS Interface Host 1 Remote 1 Host 2 Host 3 Host 4 Host 5 Remote 2 Remote 3 Remote 4 Remote 5 BTS Site A Controller Sector 1 Sector 2 Sector 3 BTS Interface BTS Interface BTS Interface Host 1 Remote 1 Host 2 Host 3 Remote 2 Remote 3 A N N N! (N-A) i i! P(>0)= A ∑ N-1 + A N N N! (N-A) i=0 New Network Architecture Page 5 Final Configuration: The estimated equipment savings realized for the service provider’s three sector simulcast application vs. a five sector application were as follows: Estimated savings in required BTS and LRCS equipment: • 7 fewer base radios required (est. as provided by customer) 7* $5,000 = $35,000 • 50% fewer LRCS-BTS Interfaces required (list, 2 primary panels) 2* $2,900 = $5,800 • 30% fewer high power TX combiners required 2* $3,000 = $6,000 • 30% less Rx Multi-coupling 2* $2,000 = $4,000 Estimated expense in required simulcast equipment: • 4 Low power splitters and combiners and coaxial leads 4* $400 = $1,600 Savings realized by converting four sectors to two simulcasts: Total Equipment Savings = $49,200 (less expenses) Additional operational savings: • Reduced BTS space and power requirement (less equipment) • BTS Ops/Field/Perf/Design Engineering support (fewer RF channels) BTS Site A Controller BTS Site B Controller Sector 1 (6RFc) Sector 2 (9RFc) Sector 3 Sector 4 (9RFc) Sector 5 BTS Interface BTS Interface BTS Interface BTS Interface BTS Interface Host 1 Remote 1 Host 2 Host 3 Host 4 Host 5 Remote 2 Remote 3 Remote 4 Remote 5 Additional Benefits of Simulcast Simulcast networks also can substantially reduce required switch and handoff processing and further improve trunking efficiencies within a given coverage area. In addition, assigning simulcasts where there are sequential busy hours between radiating points (i.e.: a sports stadium, a mega mall, and a business area may all have differing busy hours) can also greatly enhance revenue per base radio due to an increase in duration of peak minutes of use (MOU). In this urban market application, the service provider's simulcasts will require less BTS infrastructure, reducing base radio and RF interfacing equipment and potentially reducing required base site controllers and required T1 lines to the switching office as well. BTS can consolidate to central locations. It virtually eliminates dropped and poor-quality calls associated with the “ping pong” handoffs commonly experienced in urban environments. Another benefit that impacts the entire network is the substantial opportunity to greatly reduce co- channel/pilot pollution interference issues and optimize re-use by judicious use of simulcast. This is particularly true in the network core where it enables the service provider to achieve the desired metro core in-building signal penetration while virtually eliminating under- utilized urban channel sets. This has a tremendous impact for the service provider by more efficiently using existing allocated spectrum while improving call quality with lower co-channel interference throughout the network (less C/I interference). Conclusions Digivance networks configured in simulcast deliver service providers a greater return on investment by creating the optimal traffic management scenario of improved base radio utilization (i.e. more Erlangs per base radio) and increasing MOU income per base radio. As service provider channel capacity dictates, larger simulcasts of four or six or even more Digivance links can provide still greater network savings while delivering unprecedented network coverage quality. In conclusion, this service provider’s urban market application of a Digivance digital simulcast network significantly enhanced network coverage and capacity in an urban core environment. The more efficient use of RF frequency resources allows for future growth in services while reducing the need for an expensive and intrusive network allocation of additional RF bandwidth. New Network Architecture Page 6 New Network Architecture Page 7 ADC Telecommunications, Inc., P.O. Box 1101, Minneapolis, Minnesota USA 55440-1101 Specifications published here are current as of the date of publication of this document. Because we are continuously improving our products, ADC reserves the right to change specifications without prior notice. At any time, you may verify product specifications by contacting our headquarters office in Minneapolis. ADC Telecommunications, Inc. views its patent portfolio as an important corporate asset and vigorously enforces its patents. Products or features contained herein may be covered by one or more U.S. or foreign patents. An Equal Opportunity Employer 102114AE 1/06 Revision © 2002, 2004, 2006 ADC Telecommunications, Inc. All Rights Reserved Web Site: www.adc.com From North America, Call Toll Free: 1-800-366-3891 • Outside of North America: +1-952-938-8080 Fax: +1-952-917-3237 • For a listing of ADC’s global sales office locations, please refer to our web site. WHITE PAPER . New Network Architecture Digivance ® Simulcast Networks Reduce Network Costs and Improve Quality of Service WHITE PAPER Improving Grade of Service. Costs and Improve Quality of Service New Network Architecture New Network Architecture Page 3 What is " ;Simulcast& quot;? A wireless simulcast communications