Two worlds collide. The inevitable, imminent convergence of mobile transport and fixed access networks. White paper. 1 Technical white paper

Transcription

1 The inevitable, imminent convergence of mobile transport and fixed access networks White paper 1 Technical white paper

2 Contents Introduction 3 The forces behind the 5G network modernization 3 The complementarity of mobile and fixed networks 7 Virtualization and the software-defined network 8 Fiber for the future of backhaul 9 Forward-looking 10 Network sharing strategies 11 Conclusion 12 2 Technical white paper

3 Introduction A few years ago, many predicted that the rapidly increasing demand for mobile services would reduce the importance of fixed networks, if not render them obsolete. However, the opposite is becoming true. We have reached a point where mobile operators cannot efficiently meet rising demand without relying on fixed broadband networks. On one hand, Long Term Evolution, LTE Advanced (pro) (4.x) and 5G standards introduce new architectures and new interfaces with a new set of requirements, challenging transport networks to deliver more capacity at lower delays. On the other hand, operators realize that RAN network modernization requires innovative fiber transport solutions in order to keep costs under control. The most resource efficient approach for mobile transport is leveraging fiber-to-the-home (FTTH) networks which serve as an enabler in areas where 5G capacity will be needed the most. Fiber access networks are thus becoming a strategic differentiator for mobile services. Owner-operators of mobile networks can benefit from closer collaboration with fixed network operators because they face a very complementary set of challenges. Both types of network must keep pace with increasing demand: more subscribers, generating more traffic and wanting faster connections. On the fixed front, fiber is being brought closer and closer to end-users. The resulting increase in street cabinets and nodes perfectly matches the cell densification strategy being pursued by mobile operators. By joining forces, the 5G mobile transport network is already in place: fixed operators deliver faster network monetization and expedite their FTTH deployments while mobile operators have a cost-effective mobile transport solution in the areas where wireless congestion and expansion will occur. The forces behind the 5G network modernization There are 3 important trends taking place as networks evolve towards to 5G architectures. Advances in mobile technology with widely varying requirements for low latency and high throughput. New spectrum above 6GHz increases densification of mobile access networks, with more cells with shorter radius. Centralized and virtualized (Cloud) RAN architectures for improved cell coordination and lower total cost of ownership. 3 Technical white paper

4 Advances in mobile technology LTE Advanced (pro) 4.x and 5G introduce new challenges for transport networks. Future mobile networks will no longer be designed for a single traffic type but for multiple types with different requirements. 5G will be a new radio access technology family that expands to multiple dimensions by providing a common ground for numerous radio technologies (cellular, Wi-Fi, fixed), multiple applications and multiple network operators. The applications of 5G are usually segmented into 3 types: Enhanced mobile broadband (embb) for users offering Gigabit services whenever needed with 10,000 times more traffic, ubiquitous availability, and high user-mobility. Ultra-reliable, low latency communications (URLLC) for mission-critical applications such as vehicle-to-x (V2X) or automated manufacturing (Industry 4.0). This requires guaranteed availability and reliability of the radio link as well as transmission latency values down to 1 ms. Massive machine-type communications (mmtc) providing radio links for huge numbers of sensors that only occasionally transmit small amounts of data, preferably with strongly reduced signaling overheads as compared to embb and URLLC. One of the main effects on mobile transport will be to become more dynamic to handle different types of services, with widely varying requirements for mobility, reliability and latency, as explained above, as well as energy efficiency. For instance, enhanced mobile broadband will require huge capacity and video caching capabilities. Massive IoT will instead need high density but without mobility. And mission-critical applications will be more about low latency and high reliability. To address the requirements of various 5G applications, the concept of network slicing is introduced, whereby the 5G physical network is sliced into parallel and independent, logical end-to-end networks, with each slice dedicated to a specific set of requirements. This approach allows the efficient delivery of simultaneous services with widely differing needs for bandwidth, latency and reliability within a unified network deployment. Operators also want the ability to monetize offerings to large customers and verticals whose devices or traffic may have specific service characteristics. On the transport side, this implies a need for increased service awareness and flexibility. 4 Technical white paper

5 Figure 1. Mobile network evolutions >10 Gb/s peak data rates Unlimited experience Mb/s whenever needed <10 ms E2E latency Extreme mobile broadband 10,000 x more traffic x more devices 5G M2M ultra low cost 10 years on battery For everything Massive machine type communication Ultra-reliable low latency communication Instant action <1 ms E2E latency Ultra reliability Modernization of 4G networks Disruptive solutions are needed to deliver more capacity and lower delays while keeping costs under control Subscriber and traffic growth More cell capacity More radio cells More spectral efficiency Massive MIMO and multiple sectors raise the cell throughput LTE macro umbrella and 5G new radio cell densification Interference cancellation schemes with multi-connectivity between LTE and 5G User experience and peak throughput C-RAN evolution Cloud RAN is the evolution towards 5G Centralized and virtualized to reduce TCO and improve cell coordination Densification and centralization has huge challenges for the transport network Increasing capacity and density In order to deliver on the low latency and high throughput promises, 4.x and 5G access networks will require more spectrum and above 6 GHz spectrum requires increasingly densified cells. There will be more cells, each with a shorter radius (i.e. small cells), a mix of access technologies and a generalization of high-capacity standards such as 10 Gb/s Ethernet interfaces. As a consequence, there is increased pressure on installation simplicity and reduced footprint to contain the total cost of ownership. Radio access technologies (RAT) are distinguished by their frequency ranges, lying either below or above 6 GHz. Particularly in the case of carrier frequencies in the multiple 10 GHz range (mmwave), the signals are transmitted using multi-antenna arrays that allow for beam forming and user tracking, thus minimizing interference and maximizing the channel throughput. 5 Technical white paper

6 Centralized RAN architectures as a basis for virtualization and Cloud RAN The evolution towards 4.5G, 4.9G and ultimately 5G will bring updates in the RAN. Several architectures will likely coexist in future networks. With coexistence in the same areas, advanced multi-cell interference management and coordinated transmission schemes are possible to improve spectral efficiency. It can be difficult to implement these on traditional distributed RAN architectures. Traditional RAN architectures, where both the radio and baseband functions are located at the cell site, will be complemented by centralized RAN architectures. In a centralized RAN, the baseband functions are split from the radio and centralized, introducing new transport interfaces. This interface can be based on the Common Public Radio Interface (CPRI) standard in dense areas and countries where fiber is widely deployed (CPRI being bandwidthhungry with a constant bitstream). In cloud RAN architectures, part of the baseband functions is hosted in the cloud, with the intent to exploit network function virtualization (NFV) capabilities. In this case, an Ethernet-based next-generation fronthaul interface is introduced with a variable bitrate that permits statistical multiplexing and allows the use of traditional fixed access network technologies such as switched Ethernet and Passive Optical Networks (PON) technologies. 5G networks are expected to employ, to a large extent, Virtualized Cloud (hence centralized) radio access network (C-RAN) architectures in which the digital data processing functions within the baseband are distributed among central units and distributed units at the antenna sites. Depending on the specific functional split of the processing chain, the resulting anyhaul interface (anyhaul = backhaul, fronthaul, or next-generation fronthaul) will impose substantially different requirements on capacity, traffic dynamics and latency of the fixed network connecting central and distributed units. Figure 2. Mobile layer innovations drive mobile backhaul evolution Mobile anyhaul Traditional backhaul Radio and baseband unit Remote radio Traditional backhaul Remote radio Virtualized BBU Cloud packet core * Split-processing More sites More spectrum Centralized RAN CPRI fronthaul Static connectivity Ultra-low latency Cloud RAN Baseband pool Static connectivity Traditional backhaul NG fronthaul* Backhaul Backbone Dynamic connectivity Time-sensitive Ethernet Static connectivity Dynamic connectivity Cloudification Dynamic connectivity Packet core Packet core Data center/peering 6 Technical white paper

7 The central units for digital data processing shall be virtualized and run on a cloud infrastructure, reducing the total cost of ownership of the solution. The introduction of virtualized functions, centralized intelligence in the cloud and SDN programmable interfaces enables the rapid creation, optimization and termination of services needed in the 5G era. In a 24-hour period, there is a clear complementary pattern between residential (indoor) peak use and mobile (outdoor) busy hours. For example, baseband processing power can be allocated to wherever there is most demand: residential areas in the mornings and evenings and to business areas during working hours. The complementarity of mobile and fixed networks Traditional transport solutions will have a hard time keeping pace with these evolving requirements while, at the same time, keeping costs under control. Mobile operators have traditionally relied on dedicated networks to connect their cell sites to their core networks, but they now have the opportunity to reduce costs by handing off mobile traffic to the fixed network. In urban areas, 5G radio deployments will use cmwave and mmwave spectrum with 150 to 300 radio sites per km². These radio site densities may seem high compared to today s 4G networks, which are 10 times less dense with 20 to 30 radio sites per km². However, comparable urban FTTH networks support up to 3,000 connections per km². This means that the fiber connections for 4G and 5G cells represent, respectively, 1% and 10% of the total number of fiber connection points. The massive throughput and cell densification strategy make 5G a perfect match for existing FTTH deployments. The tenfold densification is a huge leap for mobile operators. But it s a very small step for fixed network operators, as FTTH networks have, by design, the headroom to connect the additional small cells. As shown on Figure 3, operators roll out fiber networks for business and mobile transport services in the areas where fixed networks already exist for delivering triple-play services to residential users. This makes fixed networks ideally suited to supporting backhaul of the additional cells that 5G mobile networks will need. Figure 3. Overlaying fixed and mobile connection points in urban areas Fiber-to-the-premises (business services) Fiber-to-the-home (triple-play services) Fiber-to-the-cell (mobile transport) 7 Technical white paper

8 But, besides a complementary footprint, there are other opportunities for a converged fixed-mobile network. Scalability. With increasing numbers of subscribers craving and filling more bandwidth, the 5G backhaul network must be able to scale. This is a core strength of fiber access networks as successive generations of PON technologies provide capacity increases on the same infrastructure. Resiliency. High availability equipment and network resiliency are crucial to ensure the subscriber s quality of experience (QoE). Fixed networks support equipment redundancy, network resilience, feeder route diversity and MPLS path protection to enhance service availability. Quality of service. Current fixed networks already meet the quality of service (QoS) needs for video, voice and data, which are very similar to those needed for mobile backhaul (MBH) for 5G. While pursuing residential broadband, fixed operators have actually been deploying a backhaul-ready infrastructure with prime QoS and multiservice transport capabilities. Synchronization. The mobile backhaul network must support both packetbased and physical layer synchronization techniques where access to external sources is unavailable or prohibitively expensive. PON networks support a combination of built-in architectural features and efficiently tuned algorithms for synchronization. Virtualization and the softwaredefined network The software-defined networking and network function virtualization (SDN/NFV) evolution occurring simultaneously in fixed and wireless networks further increases synergies. SDN/NFV techniques can be applied in the fixed access domain to create a new way of sharing infrastructure. This is the concept behind Fixed Access Network Sharing (FANS), a technique that uses virtualization to slice the access network and providing independent control of each slice. Independently managed slices of the network can be defined for business, residential or mobile backhaul services. Providing a flexible software-programmable network infrastructure gives greater granularity and dynamicity than engineered partitioning. For wireless traffic to reliably share link capacity with residential network services, network element functions will need to be dynamically reconfigured in response to changing traffic patterns and the low latency needs of 5G applications. Moreover, it ensures that mobile network operators run and operate mobile services independently on top of a virtual but dedicated network infrastructure. 8 Technical white paper

9 The introduction of virtualized functions will enable the rapid creation, optimization and termination of services needed in the 5G era. With centralized intelligence, the fixed access network can be further optimized by making use of the centralized intelligence of the mobile network. The central units of the fixed access domain run virtualized OLT (volt) functions and the central units of the mobile access domain run virtualized BBU (vbbu) functions. In some cases, the virtualized functions of the volt and vbbu are hosted in the same cloud infrastructure. As they are both access network technologies, similar principles apply, and one has to consider where virtualization makes sense and how the virtualized network functions can be distributed for optimum performance and economics. Non-real-time application features and management functionality can be hosted in the data center, while some of the more time-critical functions can be hosted in a cloud facility closer to end users, called the Edge Cloud (see Figure 4). This delivers a new way of working, where vendors and service providers collaborate in open software frameworks and optimize the end-toend behavior across the network via programmable interfaces, which is one of the key advantages of SDN. Figure 4. Evolution towards cloud and converged access ICT Partner cloud Evolution towards cloud and DC Enterprise cloud Core Telco cloud Core cloud Edge cloud architecture Converged access and radio cloud Edge cloud Converged access and SDN Short wires Long wires Short waves Access domain 5G radio and NG PON access NG PON 10G symmetric speeds XGS-PON/TWDM-PON Evolve to 25G/100G PON Fixed access Access remote Mobile access 5G radio Massive MIMO/CA 5G new RAT mmwave Fiber for the future of backhaul Passive Optical Networks technology is one of several fiber-based alternatives in the access domain for mobile transport. PON is a point-to-multipoint architecture: the feeder fiber, optical splitter and Optical Line Terminal (OLT) port are shared between multiple users, greatly reducing the cost of deploying and maintaining the broadband access network. Therefore, PONs are popular for providing fiber-based Internet access to residential subscribers. There is a considerable likelihood for PON interfaces being available for mobile backhaul 9 Technical white paper

10 in many areas. Connecting radio cells to a nearby FTTH network results in the lowest total cost of ownership, as the incremental cost of backhauling cell site traffic over an existing PON network is less than the cost of building a separate overlay network. Converged-access strategies reduce the cost of mobile backhauling by 50% and can be achieved with point-to-point pre-aggregation or point-to-multipoint PON technology 1. Forward-looking As mobile operators deploy 4G, 4.x and eventually 5G, FTTH networks will need to increase capacity by upgrading from GPON (currently the most widelyused PON technology) to next-generation PON technologies. This can be a measured, gradual migration, where the unparalleled scalability of PON assures a compelling business case for using fixed networks for mobile backhaul. XGS-PON provides the capacity (10 Gb/s and higher) and quality of service in a far more reliable and economical way than current mobile backhaul alternatives. The flexibility of XGS-PON makes it possible to scale the network and extend beyond backhaul with 5G-ready transport options for fronthaul. TWDM-PON takes things even further. Deploying multiple wavelength pairs with TWDM-PON increases capacity to 40 Gb/s. Each pair can be configured as either 10/10, 10/2.5 or 2.5/2.5 Gb/s. Separate pairs can be used for different services (residential, business, backhaul) or even allocated to different service providers (Figure 4). The mobile backhaul service can have its own bandwidth on a wavelength pair and can evolve independently at its own pace on the same PON infrastructure. Today s PON technologies can accommodate foreseeable mobile backhaul bandwidth needs. As the need for more bandwidth grows, more bandwidth can be gradually introduced into the network, ensuring a future-ready investment for operators. Figure 5. Multiple services on a single fiber fixed access infrastructure Small cell backhaul Backhaul increasing cell sites volumes and traffic, over existing residential network Next-gen fronthaul Add more wavelengths to cover more services or boost their bw TWDM tunable (10/10 or 10/2.5) TWDM tunable (10/10 or 10/2.5) TWDM tunable (10/10 or 10/2.5) P2P XGS (10/10 or dual-rate 10/10+10/2.5) GPON Remote node backhaul P2P Unified access XGS dual-rate Optimize by mixing P2P and PON topologies with different split ratios Maximize investments by multiplexing residential, enterprise and mobile services 1 Further reading: The business case for using residential broadband for mobile backhaul 10 Technical white paper

11 Network sharing strategies Service providers of every kind are increasing investments to expand their reach and improve speeds for customers. The monetization of their assets and return on investment are, to some extent, even more important than choosing which technology to use. Operators can consider 3 different levels of sharing fixed network assets for mobile backhaul: spatial, spectral and temporal. Figure 6. Network sharing strategies Fiber surplus Dedicated P2P or PON Spare fiber in ducts or cables Share pole and ducts Spatial sharing Multi-service transport network GPON XG-PON XGS-PON Packet statistical multiplexing Temporal sharing ODN Wavelength Division Multiplexing Spectral sharing Overlay with P2P wavelengths DWDM CWDM Spatial Co-existence with TWDM-PON Spatial sharing simply means running dedicated, parallel infrastructure for each service but sharing common outside plant like ducts and poles and potentially even cables, though maintaining separate fiber lines for each service. This option nicely segregates operations at the expense of duplicating active equipment. Operators can also share the same access platform but not the same cables by having a dedicated PON for backhaul services. In this case, reduced split ratios (1:4 or 1:8) can be used for backhaul, such that the PON bandwidth is shared between fewer connection points. Spectral Spectral sharing means using the same physical fiber for all services but giving each service a separate, dedicated wavelength. This technique can use different P2P WDM technologies such as Coarse Wave Division Multiplexing (CWDM) and WDM-PON for each service. However, P2P and P2MP technologies cannot be combined without investing in separate fibers or additional wavelength multiplexers to separate traffic. This is a more complex solution that restricts future scalability of the network. 11 Technical white paper

12 Temporal The most cost effective solution is to share both the access equipment and the fibers of the outside plant; a passive point-to-multipoint solution is OPEX friendly with only passive splitters (compact size and no power) and a minimum amount of fiber strands to maintain. This can be achieved via temporal (time) sharing: using the same transportation technology on the same fiber with services allocated to different timeslots. Timeslots can be fixed for fully segregated services, but the most cost effective technique is dynamic allocation. Services can be dynamically mixed based on statistical multiplexing and the oversubscription of the medium. There are two ways to do this: Multiplex Ethernet packets of different services on the same PON. Even on heavily loaded GPONs that are popular for residential FTTH services, there will generally be more than 1 Gb/s headroom left for adding one or two cell sites. This is particularly effective, and easy to achieve, for urban and sub-urban cell sites (e.g. rooftops of offices or multi dwelling units). Ethernet packet networks take advantage of bandwidth dynamics (bursty traffic and day/night cycles) via statistical multiplexing between FTTH and FTTCell traffic: FTTH traffic mainly peaks during the morning and evening while mobile cell traffic mainly peaks during the day. Next-generation PON (such as XGS-PON) fulfills demands for Gigabit peak throughput and will support the higher symmetrical bandwidth required to support 5G backhaul requirements. Deploy multiple wavelengths with TWDM-PON. TWDM-PON adds additional P2MP wavelengths on the same PON infrastructure. Bandwidths can be allocated flexibly for each wavelength and each can evolve independently. Wavelengths can also be unbundled and assigned to additional operators, which promotes co-investment opportunities that allow operators to effectively share a common infrastructure but manage, control, and operate their own dedicated wavelength. This significantly lowers the costs and risks of deploying a fiber network and creates an easy way to increase the addressable market, with the same investment. Conclusion The evolution towards 4G, 4.x and 5G networks will introduce new demands on transport networks. The telecommunications industry agrees that future mobile evolutions are increasingly dependent on the availability of cost effective and geographically widespread backhaul solutions. Passive optical networks for FTTH will become a very popular technology for Ethernet fronthaul and backhaul thanks to the cost-effectiveness of sharing the installed base of fiber infrastructure. Next generation PON with 10 Gb/s (or even 40 Gb/s) and low latency configurations will be vital for supporting the necessary levels of coverage, capacity and latency required by 5G. 12 Technical white paper

13 Figure 7. Wireless complements fixed, fixed complements wireless Small cell backhaul 3G/4G macro Wi-Fi hot spot Metro cell 5G Next-gen fronthaul Indoor small cells Hybrid CPE FTTdp FTTH FTTP FTTdp FTTH FTTH FTTP FTTB FTTH Fixed wireless access ISAM OLT Metro and small cells Bring TCO down Deploy on top of today s network Deliver on the promise of 5G More dense Push ARPU up Deep fiber penetration C-RAN, LTE-A, 5G Explosive mobile traffic growth MBH, fronthaul, anyhaul, Wi-Fi offload More diversified Technology evolution Rapid bandwidth increase FTTH, FTTN, FTTdP, FTTB, HFC Vectoring, G.Fast TWDM-PON, R-CCAP Gigabit Networks with up to 10 Gb/s for residential users The mobile operator perspective The fixed operator perspective Nokia continues to evolve with ground breaking innovations in products and professional services. Nokia s fixed networks provide the optimal user quality of experience, consistent with the business goals of the service provider, and can provide the lowest total cost of ownership by converging mobile backhaul services with today s residential broadband networks. This is achieved through unmatched flexibility in deployment models and massive scalability to accommodate growing traffic and base station numbers. With fixed networks, everyone wins. Converged operators who own both fixed and mobile assets will improve their business case. Mobile operators with plans to acquire or enter a joint venture with fixed operators can then compete with incumbents. Mobile operators already preparing for 5G keep backhaul costs under control. Fixed operators have a catalyst for delivering faster network monetization and expediting FTTH deployments. Wholesale fixed operators can add high-revenue business and increase revenues. 13 Technical white paper

14 Network operators who have deployed the Nokia Intelligent Services Access Manager (ISAM) platform for residential broadband services have a strategic platform in place to provide cost-effective mobile backhaul. With superior investment potential towards high bandwidth next-generation PON and lowlatency next generation fronthaul evolutions, the Nokia ISAM portfolio fits not only the current needs for mobile backhaul but addresses also future cloud RAN requirements. To learn more about Nokia fixed networks for mobile transport, please visit our website. 14 Technical white paper

15 Nokia is a registered trademark of Nokia Corporation. Other product and company names mentioned herein may be trademarks or trade names of their respective owners. Nokia Oyj Karaportti 3 FI Espoo Finland Tel (0) Product code: SR EN (May) 2016 Nokia nokia.com