1. The Future of Software Radio: Wireless Network Cloud
Parul Gupta, Smruti Sarangi, Shivkumar Kalyanaraman [IBM Research – India]
Zhen Bo Zhu, Lin Chen, Yong Hua Lin, Ling Shao [IBM Research – China]
The Future of Software Radio: Wireless Network Cloud
IBM Confidential

2. Outline
Cellular wireless systems and convergence trends (esp in emerging markets)
Today’s 2G/3G architectures and the trend towards 4G (all-IP and OFDMA for PHY/MAC layers)
Increasing computational costs, low utilization with future generations of technology, upgrade cycles, growing maintenance / OPEX costs.
SDR evolution:
Firmware OTA upgrades on vendor platforms,
From DSP/FPGA platforms to Hybrid IT platforms,
Multi-technology / multi-operator support
Virtualization & cloud given fiber-to-tower availability
IBM Confidential

3. Wireless: short technical summary
Scarce bandwidth
( MHz/operator)
Rate
Mobility 2G 3G 4G
802.11b
WLAN
2G Cellular
Other Tradeoffs:
Rate vs. Coverage
Rate vs. Delay
Rate vs. Cost
Rate vs. Energy
3. Tradeoffs: Rate vs X
(no free lunch!)
2. Spectral Efficiency:
MHz -> Mbps (signal to noise ratio is key!)
Today With femto cells & MIMO antennas
Wireless networks are designed to maximize spectral efficiency, support mobility, coverage, and Quality-of-Service under severe spectrum/bandwidth constraints
In emerging markets the dependence on wireless is high and growing.
ARPU pressures are severe: $2 incremental ARPU today.
Operators aggressively outsource their (wireless/wired) networks and IT.
Wireless IT convergence
IBM Confidential

4. Wireless Convergence: Closed Vertically Integrated to Horizontal Open
Apps: Unified Comms (multimedia),
Smarter Planet, mobile VAS, Internet apps, Spoken Web/SMS platforms…
Convergence at
Application/Solutions Level
Circuit Voice;
Data overlay
Middleware: IMS, SDP
Integrated MAC,
network functions
Convergence at
Network Services Level
Network layer: IP
TDMA/CDMA
Convergence at
Systems Level
Radio layer: OFDMA/MIMO
2G/3G wireless
4G wireless
System: IT and wireless systems are approaching similar system architectures
Network Services: Convergence of enterprise wireless and operator wireless services
Application/Solutions: Seamless integration and interaction of wireless infrastructure and mobile applications
There is another interesting twist in this wireless / IT convergence at the systems level
IBM Confidential

5. 2G-3G wireless network architecture
PSTN
2G-3G wireless network architecture
4G Wireless Network over Wireless Network Cloud
Cloud of Wireless Access Network + Core Network
Access Network
Core Network
Service Network
SMS/MMS
WAP GW
SMS/MMS
IMS
Content Service
Web Service
Mobile switch center BS
BS cluster
Radio network controller BS
Edge gateway
Management Server
Service support node
Radio network controller
Gateway
Billing
Edge gateway BS
Internet
BS cluster BS
IBM Confidential

6. 2G/3G/4G Wireless over Wireless Network Cloud
PSTN
2G/3G/4G Wireless over Wireless Network Cloud
Service on Edge
Cloud of Wireless Access Network + Core Network
Service Network
SMS/MMS
IMS
Content Service
Web Service
BS cluster
Edge gateway
Management Server
Service support node
Billing
Edge gateway
Internet
BS cluster
IBM Confidential

7. Mobile Infrastructure Network Hierarchy
Core Network
Radio Access Network
Challenges: The radio access network is a costly and continuous investment ($100B+).
With reducing ARPUs and need for broader nationwide coverage, there are more
initiatives for sharing infrastructure
IBM Confidential

8. Various Forms of Infrastructure Sharing in Wireless Networks
Network Sharing (eg: rural)
Base Station Sharing (leads to cloud)
BSC
Owner #1
Retail
Owner #1
Network
SDR
RRU
MSC
BSC
BTS
BSC
Owner #2
Retail
Owner #2
Network
Base Band Unit
BTS
Antenna Sharing
Tower Sharing (very popular)
BSC
BTS
Owner #1
Network
BSC
BTS
Owner #1
Network O
BSC
BTS
BSC
BTS
Owner #2
Network
Owner #2
Network
IBM Confidential

9. Towers: Passive vs Active Infrastructure Sharing
IBM Confidential

10. Passive Sharing and Tower Companies
Eg: Indus Towers (JV controls towers of Bharti, Vodafone, Idea) has 100K towers.
Tata Teleservices, Aircel have signed deals with BSNL for sharing 60K+ towers.
IBM Confidential

11. Towards Active Sharing: Unbundling Base Stations: RRU + BBU
Distributed base station
RRU (Remote Radio Unit)
BBU (Base Band Unit)
Two key standards enable distributed base station development
CPRI
OBSAI
Benefits of distributed base station
Reduce cost of facilitate infrastructure
Reduce power consumption
Easy of installation
Flexible deployment model
Traditional Integrated Macro BS
RRU
BBU
Distributed BS: RRU + BBU
IBM Confidential

12. Distributed base station deployment #1: under the tower
Scenario #1: Unbundle at the tower
MSC
RRU
RRU
<100m
BSC
5-10Km
RRU-BBU Distance <100m
5-10Km
BBU
BBU
70% - 80% power consumption is RRUs
3 RRU: 100 – 150W/RRU
1 BBU: 100W
Requirement & Challenges to BBU
light weight < 10Kg
small size (1U – 2U)
low power consumption (< 100W)
IBM Confidential

13. Software Radio & Software Defined Radio: One way of BBU impln
IBM Confidential

14. Multi-Technology Software Radio: 1 BBU Bladecenter vs 5 boxes
IBM Confidential

15. Multi-Operator Base Station with Software Radio
IBM Confidential

16. Active Infrastructure Sharing: Field Trial in India (IBM/partner)
IBM Confidential

17. Unbundled SDR BS w/ Open Wireless Interfaces & IT Platforms
IBM Confidential

18. Distributed base station #2: distributed RRU + centralized BBU pool
Scenario #2: central deployment
BSC
BBU Pool
RRU
BBU
MSC
10KM
Benefits
Fit for super urban, urban with high density of traffic
Highly scalable
Improve utilization by resource sharing
Reduce management cost
Requirements & Challenges to BBU
High density
Resource sharing with BBU pool
Low power consumption
Key barriers:
Fiber distance (<10Km)
Increasing IO data throughput >10Gbs with LTE
Fiber construction cost
Synchronization in long distance network
Case in China:
World largest TD-SCDMA BBU pool
Max support 72 RRUs
Power: 400W
A city like Bangalore or Delhi could be served from <10-15 pooled sites.
IBM Confidential

19. IT & Cloud Computing Techniques
Wireless Network Cloud: Convergence of IT Platforms, SDR & RRH, Cloud Computing Principles & Fiber-to-the-tower
Software Radio Technology/
Hybrid IT Systems
IT & Cloud Computing Techniques
Remote Radio Header Technology
BaseStation Pool
Antenna + Remote Radio Header
Fiber (> 10Km)
Wireless Network Cloud
End-to-End IP Infrastructure in 4G
IBM Confidential

20. Multi-cell environment with frequency reuse factor 1
Wireless Network Cloud Potential: Distributed Interference Management. Eg: Collaborative MIMO for Elastic Capacity Allocation
Multi-cell environment with
frequency reuse factor 1
Optical fiber
Optical fiber
interference
Optical fiber
Multiple points collaborate to mitigate ICI
or align interference for cancellation.
IBM Confidential

21. An e2e Demo has been setup in IBM CRL/IRL (WiMAX@2.4GHz)
Collaboration of IBM China and India Labs:
Multiple base-stations on common IT platform, USRP & e2e flows
IBM Confidential

22. BS SDR System Architecture
MAC: Software Components
Control & management
Switch of BS system
BS edge router
MAC instance
Adapter
MAC and adapter Stacks
Scheduling
Fragment & packing
Packets Encryption
Concatenation
Packet Extract
Defragment & unpacking
Packets Decryption
MAC Management
Downlink
Uplink
DL Adapter
UL Adapter
Msg.
Key technical challenges being addressed (IRL+CRL)
How to map the wireless software radio (SWR) stack/workload to massive multicore and hybrid architectures?
How to meet QoS and real-time requirements for the VoIP application, especially since the wireless software stack (such as PHY and MAC layer) will be implemented in software using a regular OS?
Fast path data processing
Slow path message processing
IBM Confidential

23. Laundry List of Challenges
Difference from regular computational, storage cloud: “real-time computational cloud”
Focus on very high performance, real-time synchronized behavior.
Cooperative techniques require greater degree of rigor in performance management
Wireless = Critical infrastructure. Availability / reliability equally important as real-time performance support.
Choice of underlying platforms: hybrid systems, commodity servers and mapping it to VMs (eg: MAC VM may work well on system A, and PHY VM work well on system B).
Need real-time virtual switches that can tie together such component VMs into a pipeline (Network -> MAC -> PHY)
Cooperative techniques require redesign of protocols / implementation
Multi-tenancy, elastic provisioning of real-time resources, tracking performance / availability risks (eg: 4-5 nines)
Providing backup for virtual base-stations from multiple data center sites: “cloud” attribute.
Helping the industry move from an integrated “box” model to a software + outsourced services model.
Hypothesis: ARPU pressures faced by providers will ultimately drive such a move. Aggressive outsourcing happening in markets like India.
IBM Confidential

24. Summary Software radio is an emerging technology.
The long term potential of software radio involves:
Unbundling base stations into hardware, software, RF components.
Application of IT platforms, open wireless interfaces to SDR; opening up a open-source community of developers
Allowing flexibility for BS software to be virtualized, and consolidated into pools for reduced CAPEX/OPEX, higher utilization and change business models
Fiber to towers will allow pooling and application of the Cloud model.
Wireless network cloud can provide new benefits.
Elastic capacity allocation & higher utilization/lower costs
Distributed Interference Management: Collaborative MIMO etc (5th Generation Wireless)
Integration of edge-based services at the cloud site. Eg: caching, content delivery, unified communications, enterprise app delivery, cloud-based application delivery etc
Perfect storm of “cloud” challenges:
Real-time, synchrony/performance-critical, ultra-high reliability requirements.
IBM Confidential

25. Terminology RAN – Radio Access Network CN – Core Network
BTS – Base Station = BBU + RRU
BSC – Base Station Controller
BBU – Base Band Unit
RRU – Remote Radio Unit
RNC – Radio Network Controller, BSC in 3G
NodeB – BTS in 3G
eNB – Base Station Node in LTE
LTE – Long Term Evolution (E-UTRAN)
AIPN – All IP Network
NEP – Network Equipment Provider
IBM Confidential