/1 R1 / Rafael Rodriguez Sistemas de Comunicaciones Móviles FACULTAD DE INGENIERIA U.C.V. Escuela de Ingeniería Eléctrica Design Guidelines for RF System.

Presentación del tema: "/1 R1 / Rafael Rodriguez Sistemas de Comunicaciones Móviles FACULTAD DE INGENIERIA U.C.V. Escuela de Ingeniería Eléctrica Design Guidelines for RF System."— Transcripción de la presentación:

1 /1 R1 / Rafael Rodriguez Sistemas de Comunicaciones Móviles FACULTAD DE INGENIERIA U.C.V. Escuela de Ingeniería Eléctrica Design Guidelines for RF System System Planning Traffic Analysis, Grade of Service (GOS). Sites availability, Site Survey. Power Supply System Grounding. Tower Top Amplifiers (TTA), Antenna System

2 /2 R1 / Rafael Rodriguez Sistemas de Comunicaciones Móviles FACULTAD DE INGENIERIA U.C.V. Escuela de Ingeniería Eléctrica System Design

3 /3 R1 / Rafael Rodriguez Sistemas de Comunicaciones Móviles FACULTAD DE INGENIERIA U.C.V. Escuela de Ingeniería Eléctrica Queuing Theory M/M/1 Queuing System Single Server Conceptual Model Arriving Calls Queue Departing Calls Server 

4 /4 R1 / Rafael Rodriguez Sistemas de Comunicaciones Móviles FACULTAD DE INGENIERIA U.C.V. Escuela de Ingeniería Eléctrica Some Terms Defined... Call Arrival Rate,  –Is the average number of calls made per user during the busy hour  = (calls/user) / hour * users = calls/hr Service Rate,  –Call duration = 1/  Utilization Factor,   cannot exceed 100% also known as the system offered load unitless quantity known as Erlangs

5 /5 R1 / Rafael Rodriguez Sistemas de Comunicaciones Móviles FACULTAD DE INGENIERIA U.C.V. Escuela de Ingeniería Eléctrica Queuing Theory M/M/1 Queuing System Arriving Calls Queue Departing Calls      total Servers

6 /6 R1 / Rafael Rodriguez Sistemas de Comunicaciones Móviles FACULTAD DE INGENIERIA U.C.V. Escuela de Ingeniería Eléctrica Some Terms Defined... M/M/mMemoryless arrival process/ memoryless service process/ number of servers. ErlangsDimensionless quantity whose numerical value is a measure of the demand on the system.  = Call Rate * Mean Call Duration GOS Grade of Service; probability that a call will be queued or blocked. GOS = f {Erlangs}

7 /7 R1 / Rafael Rodriguez Sistemas de Comunicaciones Móviles FACULTAD DE INGENIERIA U.C.V. Escuela de Ingeniería Eléctrica The Erlang Analytical Tools Erlang C Analysis –Assumptions: System which queues calls Poisson process of call arrivals exponentially distributed interarrival times and service times Solution gives the probability of queuing

8 /8 R1 / Rafael Rodriguez Sistemas de Comunicaciones Móviles FACULTAD DE INGENIERIA U.C.V. Escuela de Ingeniería Eléctrica The Erlang Analytical Tools Erlang B Analysis –Assumptions: System which does not queue calls, blocking system Poisson process of call arrivals exponentially distributed interarrival times and service times Solution gives the probability of blocking

9 /9 R1 / Rafael Rodriguez Sistemas de Comunicaciones Móviles FACULTAD DE INGENIERIA U.C.V. Escuela de Ingeniería Eléctrica Erlang Limitations Erlang C / Good approximation for voice calls only –Exponential Call Duration Data call TX times are deterministic –Queuing System Data calls do not queue –System Design Parameters Access times, delay times, retries, Bit-Error-Rate, etc,. Erlang B / Good approximation for inbound data only –Exponential Call Duration Data call TX times are deterministic –Non-Queuing System Voice calls queue –System Design Parameters Access times, delay times, retries, Bit-Error-Rate, etc,.

10 /10 R1 / Rafael Rodriguez Sistemas de Comunicaciones Móviles FACULTAD DE INGENIERIA U.C.V. Escuela de Ingeniería Eléctrica Design Goals Most important one is the GOS: –Public SafetyGOS< 1% –Utilities GOS<10-15% Adjust number of channels until required GOS is achieved

11 /11 R1 / Rafael Rodriguez Sistemas de Comunicaciones Móviles FACULTAD DE INGENIERIA U.C.V. Escuela de Ingeniería Eléctrica Design Considerations Worst Case Analysis – Design capacity for busy hour Input Parameters – Number of users (voice and data) – Number of calls/user (per busy hour) – Mean call duration – Data message size(s)

12 /12 R1 / Rafael Rodriguez Sistemas de Comunicaciones Móviles FACULTAD DE INGENIERIA U.C.V. Escuela de Ingeniería Eléctrica Where’s the Data? New System –Request for Proposal / Talk with customer –Geographic distribution / Demographics System Manager Reports – Site Statistics for busy hour – Activity Summary Report for calls/hr – Assumptions, hypothesis, or customer for number of users Existing system / Number of users –Use System Manager data for total calls/month –How many radios did customer buy? –Determine the distribution of total calls among the sites. –Hypothesis: Distribute the radios (users) among the sites according to the call distribution 

13 /13 R1 / Rafael Rodriguez Sistemas de Comunicaciones Móviles FACULTAD DE INGENIERIA U.C.V. Escuela de Ingeniería Eléctrica Determining the Profile Utilities are easiest to define... –Typical 8-hr shifts –More homogeneous as an industry Public Safety is much harder... –Several overlapping shifts –Take-home policies Industrials & SMR’s need to be examined for traffic patterns...

14 /14 R1 / Rafael Rodriguez Sistemas de Comunicaciones Móviles FACULTAD DE INGENIERIA U.C.V. Escuela de Ingeniería Eléctrica Suggested Input Values Utilities Call Type Group Individual Interconnect Outbound Data Inbound Data # of Calls 0.2 0.01 * Call Duration 4.4 seconds 4.8 seconds 60 seconds * Depends on site/system type

15 /15 R1 / Rafael Rodriguez Sistemas de Comunicaciones Móviles FACULTAD DE INGENIERIA U.C.V. Escuela de Ingeniería Eléctrica Suggested Input Values Preliminary Public Safety Call Type Group Individual Interconnect Outbound Data Inbound Data # of Calls 0.43 0.01 * Call Duration 3.1 seconds 4.1 seconds 60 seconds * Depends on site/system type (ie 1.5 for SS)