# Presentation: 388514

## Scenarios To Be Evaluated for the HDLCand CCSDS Data Link Layer Protocol Performance over a TDRSS Satellite LinkAnalysisRevision 1

*John Wesdock*
*27 September 2001*

**GSA-505**

## Outline

*Introduction*
*Simulation Model Overview*
*Simulation Scenarios*
*Simulation Outputs*
*Schedule*

## Introduction

*Objective*
*Provide an overview of the capabilities and limitations of the CCSDS and HDLC simulation models as currently implemented*
*Propose simulation scenarios to be evaluated for the purpose of fulfilling the objectives of this study*
*Obtain consensus agreement on the metrics to be measured by the simulations *
*Scope*
*CCSDS and HDLC simulation model implementations examined*
*Implementation assumptions examined*
*Implementation capabilities and limitations examined*
*Objectives of this study reviewed*
*Simulation scenarios proposed*
*Simulation outputs identified*
*Schedule reviewed*
*Simulation run-time issues discussed*

## CCSDS Framer Simulation Model

**CCSDS Simulation Statistics**

**CCSDS Framer Model*******

*CCSDS Framer Simulation Model*

- AttachedSync Marker

- Header

- Data

- FrameError Check

**Sync****Generator**

**Error****Detection****Code**
**E=f(data)**

- • To be simulated
- • Actual pattern   to be used
- •  If R-S coding to   be used, ASM   added after   R-S coding

- • To be simulated (required   fields only)
- • Random data to be used
-   (i.e., header data not
-   interpreted on receive  end - the R-S code or  Frame Error Check will  Identify errors in header)

- • To be simulated
- • Packetized random
-   data to be used

- • To be simulated   (except when
-    R-S coding is   present)
- • CRC-CCITT

**Specified CCSDS Frame**

- RandomData

- IP Packet

- * Diagram assumes no R-S coding.  If R-S coding is used, the Frame  Error Check is not included and the ASM is added after R-S coding.

## CCSDS Frame ReaderSimulation Model

**CCSDS Frame Simulation Notes**

**CCSDS Framer Model**

*CCSDS Frame Reader**Simulation Model*

- AttachedSync Marker

- Header

- Data

- FrameError Check

**Specified CCSDS Frame**

**Frame****Error****Check****Decoder**

- Frame synchstatus to BER/ThroughputEstimator

**Marker****Search**

- Reference frame clock

- Frame ErrorCheck Status toBER/ThroughputEstimator

**Bit****Comparator**

- Reference frame data

- Supplemental datato BER/ThroughputEstimator

*If R-S coded, rely on R-S decoded codeframe status to determine whether transfer frame includes uncorrectable errors (note: there is one CCSDS frame per RS codeframe)*
*If not R-S coded, rely on Frame Error Check (FEC) code to determine whether a frame includes bit errors or not (or simply compare RS decoded bits to frame reference signal) *
*Monitor received data for Attached Synch Marker (use reference signal to identify missed or extraneous ASMs)*

## CCSDS End-to-End LinkSimulation Model

**Ground Station**

**Space-to-Ground****Link**

**TDRS**

**Space-to-Space****Link**

**User Satellite**

*CCSDS End-to-End Link**Simulation Model*

**IP Packet****Generator**

**CCSDS****Framer**

**R-S****Encoder*******

**Convolutional****Encoder**

**Transmitter****Physical****Layer****Components**

- InstrumentData

- ThermalNoise

**Relay Sat****Physical****Layer****Components**

- ThermalNoise

**Receiver****Physical****Layer****Components**

**Viterbi****Decoder**

**R-S****Decoder**

**HDLC****Frame****Reader**

**CCSDS****Frame****Reader**

**Metric Estimator**

**BER/****Throughput****Estimator**

- Irrecoverable Codeword Flag

- Frame Check flag

- Frame Check flag

- Frame synch status

- Frame synch status

- Packet and packetclock to BER/Throughput Est

- Frame and frameclock toFrame Reader

- Referencedata and clock

- Reference data and clock

- Error-free packets only

- Error-free packets only

- Referencedata and clock

- * If R-S coding used, ASM   added after R-S coding

## CCSDS Implementation Assumptions

*Reference signals (i.e., originally-transmitted data, packet clock, frame clock, etc.) used to simplify the implementation*
*Reference clock signals used in simulations to identify when a new packet should have begun, when a new frame should have begun and when a new R-S codeframe should have begun*
*Loss of frame synch and loss of R-S codeframe synch can be identified*
*Performance statistics can be computed*
*Reference frame signal (originally-transmitted frame bits) can be used to identify when a frame contains errors*
*Frame Error Check (FEC) bits do not need to be processed because they simply detect bit errors, meanwhile, bit errors can more easily and quickly be identified by comparing the originally transmitted frame bits to the received frame bits*
*Frame and packet headers not interpreted*
*Reference signals primarily used to monitor when a frame should end and when a packet should end*

## CCSDS Capabilities and Limitations

*Capabilities*
*Transfer frames can be uncoded, Reed-Solomon coded or concatenated coded*
*User can select packet length*
*User can set transmitter, TDRS and ground terminal distortions*
*User can select TDRSS SSAR link or KuSAR link*
*User can obtain results assuming ASM-derived frame timing or “freewheeling” timing*
*User can select sensitivity of ASM search (e.g., 31 bits out of 32 bits need only be correct or 30 out of 32, etc.)*
*Limitations*
*Fixed-length packet used for entire duration of simulation*

## HDLC Framer Simulation Model

**HDLC Simulation Statistics**

**HDLC Framer Model**

*HDLC Framer Simulation Model*

- IP Packet

- FlagField

- Header

- Data

- FrameError Check

**Flag Generator**

**Error Detection Code**
**E=f(data)**

- • To be simulated
- • Actual pattern
-   expected to be
-   used

- • To be simulated (required fields only)
- • Random data to be used (i.e., header   data not interpreted on receive end -   the R-S code or Frame Error Check   will Identify errors in header)

- • To be simulated
- • Packetized random
-   data to be used

- • To be simulated (even   when R-S coding is   present)
- • CRC-CCITT

**Specified HDLC Frame**

- FlagField

- • Can be simulated
- • Actual pattern
-   can be used

- RandomData

**Bit****Stuffing**

- Header

- Data

- FrameError Check

**Flag****Generator****(optional)**

## HDLC Frame ReaderSimulation Model

**HDLC Frame Simulation Notes**

**HDLC Frame Reader Model**

*HDLC Frame Reader**Simulation Model*

- Frame synchstatus to BER/ThroughputEstimator

- FlagField

- Header

- Data

- FrameError Check

**Frame****Error****Check****Decoder**

**Specified HDLC Frame**

- FlagField

**Flag****Search**

- Frame ErrorCheck Status toBER/ThroughputEstimator

**Bit****Unstuffer**

- Reference frame clock

**Bit****Comparator**

- Reference frame data

- Supplemental datato BER/ThroughputEstimator

*If R-S coded, rely on R-S decoded codeframe status to determine whether some transfer frames include uncorrectable errors (note: there can be more than one HDLC frame per RS codeframe) and then rely on the FEC of each frame (or bit-by-bit comparison to the frame reference signal) to identify the exact frames with errors*
*If not R-S coded, rely on Frame Error Check code to determine whether a frame includes bit errors or not (or simply compare received bits to frame reference signal) *
*Monitor received data for flags (use reference bits to identify missed or extraneous ASMs and flags)*

## HDLC End-to-End LinkSimulation Model

**Ground Station**

**Space-to-Ground****Link**

**TDRS**

**Space-to-Space****Link**

**User Satellite**

*HDLC End-to-End Link**Simulation Model*

**IP Packet****Generator**

**HDLC****Framer**

**R-S****Encoder*******

**Convolutional****Encoder**

**Transmitter****Physical****Layer****Components**

- InstrumentData

- ThermalNoise

**Relay Sat****Physical****Layer****Components**

- ThermalNoise

**Receiver****Physical****Layer****Components**

**Viterbi****Decoder**

**R-S****Decoder**

**HDLC****Frame****Reader**

**CCSDS****Frame****Reader**

**Metric Estimator**

**BER/****Throughput****Estimator**

- Irrecoverable Codeword Flag

- Frame Check flag

- Frame Check flag

- Frame synch status

- Frame synch status

- Packet and packet clockto BER/Through Est

- Frame and frameclock toFrame Reader

- Referencedata and clock

- Reference data and clock

- Error-free packets only

- Error-free packets only

- Referencedata and clock

- * If R-S coding used, 24 bit  ASM added after R-S coding

## HDLC Implementation Assumptions

*Reference signals (i.e., originally-transmitted data, packet clock, frame clock, etc.) used to simplify the implementation*
*As was the case with the CCSDS implementation, reference clock signals used in simulations to identify when a new packet should have begun, when a new frame should have begun and when a new R-S codeframe should have begun*
*Reference frame signal (originally-transmitted frame bits) can be used to identify when a frame contains errors*
*When there are more than one HDLC transfer frames per R-S codeframe and an R-S codeframe is identified to contain uncorrectable errors, the individual FEC bits are not evaluated but rather a comparison to the reference frame signal is used to identify the frames containing the bit errors*
*Frame and packet headers not interpreted*
*Reference signals primarily used to monitor when a frame should end and when a packet should end*

## HDLC Capabilities and Limitations

*Capabilities*
*Transfer frames can be uncoded, Reed-Solomon coded or concatenated coded*
*User can select packet length*
*User can set transmitter, TDRS and ground terminal distortions*
*User can select TDRSS SSAR link or KuSAR link*
*Limitations*
*Fixed-length packet used for entire duration of simulation*

## Outline

*Introduction*
*Simulation Model Overview*
*Simulation Scenarios*
*Simulation Outputs*
*Schedule*

## Scenarios To Be Evaluated

*TDRSS SSAR and KuSAR end-to-end link simulation models to be used*
*Maximum allowable data rate per service to be used*
*User, TDRS and ground terminal distortions set to specified values per SNUG, WSC and TDRS specification documents*
*Four packet lengths to be considered*
*Three coding scenarios to be considered*

## Outline

*Introduction*
*Simulation Model Overview*
*Simulation Scenarios*
*Simulation Outputs*
*Schedule*

## Simulation Outputs

*Primary performance metrics to be measured by the simulations are as follows:*
*Science data throughput versus channel BER (10**-5** to 10**-8**)*
*Packet error rate versus channel BER (10**-5** to 10**-8**)*
*Frame error rate versus channel BER (10**-5** to 10**-8**)*
*Channel BER versus Eb/No*
*Science data throughput metric is calculated as follows:*

**Example Plot**

## Outline

*Introduction*
*Simulation Model Overview*
*Simulation Scenarios*
*Simulation Outputs*
*Schedule*

## Schedule

*Model development effectively completed*
*Uncoded and convolutional coded simulation runs expected to require a modest amount of computing time** *
*Reed-Solomon coded runs expected to take a significant amount of run-time to collect accurate statistics*
*Reed-Solomon coding forces simulations to dramatically oversample the bits thus yielding very long simulations*
*Two Sun Ultra 1 workstations to be used as well as several Sun Sparc 10’s*