DSRC uses dedicated short range communication technology to enable vehicle-to-everything communication for transportation applications. It operates on a 75MHz spectrum in the 5.9GHz band. Key applications include toll payment, parking, traffic updates, and remote driving assistance. Communication is achieved through SDMA and RTDMA configurations to avoid interference. The DSRC protocol uses a three layer architecture and synchronous TDMA MAC protocol with public and private windows to access the channel. Performance is improved through techniques like random delay counters and Markov modeling.

1. DEDICATED SHORT RANGE
COMMUNICATION FOR
V2X
Pramod Nalam

2. DSRC – V2X
 DSRC- Dedicated Short Range Communication was developed to meet all V2X
requirements
 75 MHz of Spectrum from 5.850 ~5.925 GHz
 5 MHz is reserved as the guard band
 10-MHz channels - 7
 Key Factors –
• Low latency
• Secure Transmission
• Fast Network Acquisition
• Variable data packet size
• Less error rate
 Use cases –
• Toll Fees
• Parking payment
• Dynamic Route Guidance -Road side communication like road constructions, traffic
updates, etc.,
• Remote driving guidance during Cruise Control
• Accurate location information which helps more for Fleet Management

3. DRSC – V2X

4. TRENDS AND
DEVELOPERS As on today, below are the OEMs that work on these technologies –
• GM
• Toyota
• Volkswagen
• Cadillac
• Lexus by 2021
 The above mentioned use cases requires –
• Simultaneous Internet Tethering
• Video streaming
• Strong connectivity
 160 MHz bandwidth of 802.11ac is in-sufficient for the above use cases, so we
IEEE has come up with 802.11p standard at 5.9GHz (unlicensed), which is not
widely used till today.
 The demand of Wi-Fi in vehicles has raised to 30% CAGR by 2017.

5. V2X - CADILLAC
 Cadillac introduced V2X from March-2017, in all their cars (only in USA)
 1,000 messages per second & 300 Meters distance

6. V2X - CADILLAC
 Cadillac represents, the V2X info as below -

7. V2X - Toyota
 Toyota has worked on a pilot project of V2X in 2016 at Japan
 V2X info represented as below -
V2V
Emergency Vehicle Notification
Cruise Control Communication
Collision Prevention at
Junctions

8. V2X - Toyota
 Toyota has worked on a pilot project of V2X in 2016 at Japan
 V2X info represented as below -
V2I
Dynamic Driving
Guidance
(Merge & Obstacle
Info)
Side Road Vehicle
Advisory
Vehicle Ahead
Advisory
Traffic Light Cautions
(Red Light, Signal
Change)

9. V2X - Toyota
V2P
Pedestrian Existence
Advisory

10. DSRC ECO-SYSTEM
 DSRC uses Beacon antennas and OBEs for communication.
 Vehicle-roadside communication systems supports decentralized system approach where
data is distributed and collected in a local environment.
 Communication link between vehicles and a roadside infrastructure in free traffic flow using
low-cost on-board equipment (OBE)
 Due to the short communication zones, the exact position of the vehicles can be
determined

11. DSRC
CONFIGURATIONSDSRC can be achieved through SDMA & RTDMA configurations -
 SDMA – Space Division Multiple Access
• Phased Arrays - Makes use of antennas with very narrow beams and which are able to
provide a lane-specific and very reliable up-link communication zone.
• No Data Collisions - Size of each communication zone guarantees, that not more than
one vehicle uses a communication zone for up-link transmissions
• Total available bandwidth often has to be divided into different frequency bands on
the up-link which reduces the available up-link data rate of each zone
 RTDMA – Random Time Division Multiple Access
• One communication zone is provided for all lanes
• Multi-access interference has to be reduced to a minimum by using suitable medium
access control protocols which resolves data collisions
• There is only one up-link channel, the full bandwidth can be used
• Usually leads to a higher available up-link data rate than in a SDMA approach.

12. DSRC Architecture
 DSRC has designed as 3 layered approach –
• Application Layer
• Data Link Layer
• Physical Layer

13. Synchronous DSRC MAC Protocol
 Standard DSRC Medium Access Control Protocols is derived based on Half-Duplex TDMA.
 The beacon (as primary station) offers two different types of up-link windows to the
vehicles:
 Public window:
• Can be accessed by every vehicle within the communication zone
• Beacon Service Table, holds information about the valid application and protocol
parameters
• Offers periodic updates to newly arriving vehicles by the beacon
 Private windows
• Allocation reserves for a stipulated time period for a specific vehicle
• Protects data against data collisions after addressing the vehicle
Standard DSRC MAC Protocol

14.  To avoid unnecessary delays during the address acquisition phase, it is essential to avoid
and resolve collision situations effectively. By randomly distributing the transmission of
newly arriving vehicles over several public slots the probability of data collisions can be
reduced which improves DSRC MAC Performance.
Open-Road Frame –
 DSRC MAC protocol, the TDMA protocol is based on a fixed frame structure called Open-
Road Frame.
 Consists of the following elements –
 Reader Control Message (RCM)
 Several Data Slots (DS)
 Number of Activation Slots (AS)
Asynchronous DSRC MAC Protocol
 Activation slots are used for the transmission of the ID of newly arriving vehicles
 Data slots may be used for down-link transmissions or are reserved by the beacon for
up-link transmissions
 RCM, the vehicles get to know the assignment of down-link and up-link slots

15. DSRC MAC Protocol Performance
 Key problem in vehicle-roadside communications is the multiple access interference
during the address acquisition phase: the vehicle, which enters the communication zone,
needs to access the communication channel simultaneously with other vehicles, which
may lead to data collisions and access delays.
 To improve performance and overcome
access delays and data collisions, they have
introduced –
 Random Delay Counter, which allows to
select one time slot randomly to the
newly arriving vehicles
 Markov Chain Modelling, it is possible to
describe the process of the data
exchange between the roadside station
and one or more vehicles.

16. DSRC MAC Protocol Implementation
 For a complete DSRC implementation, we can combine it as two services – Auto Fee
Collection (AFE) and Dynamic Route Guidance (DRG)
 Considering this, below is the protocol format we can undergo -
Note: In the above scenario, AFE is considered as high priority.

17. DSRC - Challenges
 Unlicensed Frequency
 Requires huge bandwidth
 Infrastructure
 Strong connectivity
 Strong security