These slides explain the Protocol Framework for 5G mmWave Backhaul Network, as a part of a project presentation for the course Telecom Architecture at Northeastern University.

1. Protocol Framework for 5G
mm Wave Backhaul
Network
- SWARNASHRUTI JUPUDI

2. Introduction
 We need a promising technology to significantly improve
the network capacity and satisfy the overwhelming traffic
demand from increased mobile devices, cloud
computing, video streaming, IOT, etc.
 We’ll need something that can provide a 1000-fold
system capacity, 100-fold energy efficiency, and 10-fold
lower latency as compared to the current implemented
technologies.
 Hence, the proposal for a 5G
mm Wave backhaul network.

3. What’s a Wireless Backhaul?
 Wireless backhaul is the wireless communication and
network infrastructure responsible for transporting
data from end users or nodes to the central network or
infrastructure and vice versa.
 It is the intermediate wireless communication
infrastructure that connects smaller networks with the
backbone or the primary network.
Fig 1: Typical Backhaul Deployment
Here, the data traffic transmits from UE2 to Micro1, and to Micro2, and then to
Micro4, and finally comes into core network.

4. What’s a Wireless Backhaul?
 Data is connected/transported to a Tier 1 Internet service
provider or a central telecom exchange by a wireless
backhaul infrastructure. It connects BS to core network
 The optimum choice for wireless backhaul technology
involves considerations such as network capacity,
expected data speed, relative cost, electromagnetic
interference and the availability of radio
frequency spectrum space
Fig 2: Typical backhaul deployment

5. MM WAVE BACKHAUL NETWORK
- Overview
 Wired backhaul is infeasible owing to the high implementation costs
 Current frequency bands won’t match the 5G traffic demand
 mm Wave has a bandwidth of 30 -300 GHz, thus occupying a wider spectral range
Advantages of mm Wave Disadvantages of mm Wave
• Larger Bandwidth
• Narrow Beam Width
• Highly Directional Waves
• Reduced Interference
• High Security
• Spectrum Reuse
• Can’t penetrate through solid obstacles
• Works mostly in LOS
• High Path Loss
• High power required for transmission
• High atmospheric attenuation

6. SYSTEM ARCHITECTURE FOR
BACKHAULING
 Centric
Small cell Base Stations (SBSs) access core network
through center macrocell BS that connects gateway
through fiber links
 Distributed
All backhaul data are relayed to a single specific SBS
instead of the macrocell BS. Data is transmitted
between established wired or wireless links amongst
adjacent SBS, connected to the designated SBS that
connects to core network through fiber links.
System overview for 5G mm-wave backhauling

7. Challenges and Design Goals
 Overcoming Path Loss
Beamforming techniques
Highly steerable beams are generated to form
directional links
 Dynamic Link Establishment
Adding flexibility to backhaul data transmission
Efficient routing process optimizing the data flow
Directional Beamforming

8. Challenges and Design Goals
 Efficient Spatial Reuse
• TDMA, Scheduling TDMA
• Full duplexing, hybrid beamforming and
multicast beamforming
• Dense small-cell scenarios using
heterogeneous infrastructure
Hybrid Beamforming and Full Duplexing

9. System framework for 5G mm-wave
backhauling
In the frame header, routing and scheduling schemes are performed for the backhaul required flows accumulated at the S-SBS
in the previous frame.
STDMA scheduling in the MAC layer is followed to assign specific time slots to different hops of every flow, where multiple
transmissions can be allocated in the overlapping time periods to fully exploit spatial reuse gain.
Hybrid beam forming and full duplex transmission, are utilized to satisfy the transmission requirements in the 5G mm-wave
backhaul system

10. MAC Protocol framework for 5G mm wave
backhaul
 The use of highly directional beam forming raises a number of new challenges in the
network design. We focus only on the medium access
 The design of MAC protocol for 5G mm wave backhaul network needs to take into
account the following requirements and challenges:
 How to design the suitable MAC framework and its frame structure.
 How to efficiently design the beam forming training to guarantee direction
alignment between two nodes including UEs, regular base stations, and sink base
stations.
 How to design the signaling framework to make sure that all the control
information can be transmitted.
 How to provide an open MAC frame to support diverse allocation scheme among
uplink, downlink and backhaul to maximize resource efficiency.

11. MAC PROTOCOL FRAMEWORK
-Overview
 Each wireless frame occupying Tm is divided into 10 sub-frames.
 Each sub-frame is divided into 8 slots, thus each time slot occupies Ts.
 In a sub-frame unit,
 The first time slot is set to be downlink time slot for beam forming
training, resource allocation indicating and other system control
signaling.
 The last time slot is set as uplink time slot for the UEs to transmit
feedback information such as the buffer state information, QoS
types, Channel Quality Indicator (CQI), etc
 The remaining six time slots can be flexibly and dynamically
allocated to downlink, uplink and backhaul transmission
according to the real-time traffic demand.
We use TDD approach to design the MAC Protocol for dynamic
resource allocation. FDD uses fixed bandwidth

12. Multi-dimensional resource allocation for
uplink, downlink and backhaul
transmission
 In the first downlink time slot of each sub-frame, the
base station allocates spectrum resources to uplink,
downlink and backhaul transmission according to the
downlink traffic demand
 The two-step resource allocation procedure.
 TDD configuration: In each sub-frame, the eight slots
can be flexibly divided to transmit on accordance to
the demands.
 Multi- dimensional spectrum resources: Assuming
fixed beam directions, we allocate time domain and
frequency domain resources to different UEs.
Uplink/Downlink/Backhaul TDD Configurations
Signaling of MAC frame structure

13. MAC PROTOCOL FRAMEWORK
- Beam Forming Training
 Beam forming training is deployed in the first time slot of sub-
frame after the downlink signaling.
 The base station transmits a beam training sequentially on each
beam, its power recorded by each user with a fixed antenna.
 Similarly, the other antenna is training during next sub-frame.
Therefore, each mobile user can select the optimal beam after
two sub- frames periods. In the last time slot, the UEs report
their beam forming training information along with the uplink
signaling.
Beam Forming Training

14. CONCLUSION AND FUTURE WORK
 To meet the ultra-large traffic and the super-massive connection requirement of
5G wireless networks, we focus on the MAC layer technologies and especially
proposed a MAC protocol framework for 5G mmWave backhaul network.
 The future work includes the mmWave backhaul routing and efficient resource
allocation algorithm.

15. REFERENCES
 Yusheng Liang, Bo Li, Mao Yang*, Xiaoya Zuo, Zhongjiang Yan, Qingtian Xue “MAC
Protocol Framework for 5G mmWave Backhaul Network”, IEEE 2016
 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4934318/
 https://www.wirelessweek.com/article/2016/03/why-wireless-backhaul-holds-key-5g
 http://www.rcrwireless.com/20160313/carriers/sprint-wireless-backhaul-tag4
 Small Cell Millimeter Wave Mesh Backhaul White Paper - Feb 2013
 Kan Zheng, Long Zhao, Jie Mei, Mischa Dohler, Wei Xiang, and Yuexing Peng” 10 Gb/s
HetSNets with Millimeter-Wave Communications: Access and Networking – Challenges
and Protocols “, IEEE 2015