Software-defined mobile network

Software-defined mobile networking (SDMN) is an approach to the design of mobile networks where all protocol-specific features are implemented in software, maximizing the use of generic and commodity hardware and software in both the core network and radio access network (RAN).

## History

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Through the 20th century, telecommunications technology was driven by hardware development, with most functions implemented in special-purpose equipment. In the early 2000s, generally available CPUs became cheap enough to enable commercial software-defined radio (SDR) technology and softswitches. SDMN extends these trends into the design of mobile networks, moving nearly all network functions into software.

The term "software-defined mobile network" first appeared in public literature in early 2014, used independently by Lime Microsystems[1][2] and researchers from University of Oulu, Finland.[3]

## Limitations of hardware-based mobile networks

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Mobile networks based on special-purpose hardware suffer from the following limitations:

* They have limited provisions for upgrades and usually must be replaced entirely when new standards are introduced.
* The individual components are not scalable in terms of performance and capacity, because the capacity of a component is fixed by the hardware implementation.
* Specialized equipment and its associated specialized software require vendor-specific training for the mobile operator's staff.
* Specialized hardware systems are usually supported and serviced by a single vendor, resulting in vendor lock-in.

## Characteristics of SDMN designs

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### Use of software-defined radio

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SDR is an important element of SDMN, because it replaces protocol-specific radio hardware with protocol-agnostic digital transceivers. While many earlier digital radio systems used field-programmable gate arrays (FPGAs) or special-purposed digital signal processors (DSPs) for calculations on baseband radio waveforms, the SDMN approach moves all of the baseband processing into general-purpose CPUs. SDMN radio systems also use hardware with publicly-documented interfaces that is designed to be readily reproducible by multiple manufacturers.

### Commodity components

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SDMN designs avoid the use of components that are specialized as to their functions or that are available from only a single vendor. This is true of both the hardware and software elements of the network.

### Software switching and transcoding

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The telephony switches of SDMN networks are software-based, including software transcoding for speech codecs.

### Centralized, distributed, or hybrid?

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A new SDN architecture for wireless distribution systems (WDSs) is explored that eliminates the need for multi-hop flooding of route information and therefore enables WDNs to easily expand.[4] The key idea is to split network control and data forwarding by using two separate frequency bands. The forwarding nodes and the SDN controller exchange link-state information and other network control signaling in one of the bands, while actual data forwarding takes place in the other band.

## Advantages of SDMN

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The SDMN approach has many advantages over hardware-based mobile network designs.

* Because SDMN hardware is protocol-agnostic, upgrades are software-only, even across technology generations. In the radio network, these changes can even be made on a site-by-site basis.
* Because SDMN hardware is designed to be easily sourced and reproduced:
* SDMN equipment can be serviced by a wider range of vendors, lowering maintenance costs.
* SDMN equipment can be manufactured anywhere in the world, lowering production costs.
* Because SDMN software is based on commodity operating systems and development tools:
* Support staff can be trained more quickly because they are already familiar with the underlying software systems.
* Many aspects of the SDMN can be monitored and managed with pre-existing tools, because they are already available in the commodity operating systems.
* Because SDMN network components run on general purpose computers, the network components can be scaled up in capacity by adding more computing power.

## References

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1. ^ http://www.limemicro.com Lime Microsystems
2. ^ http://secure.marketwatch.com/story/lime-microsystems-bladerf-legba-partner-on-first-software-defined-mobile-network-2014-04-30 Lime Microsystems: bladeRF, Legba partner on first software defined mobile network
3. ^ https://sites.google.com/site/callforchapterssdmn/ Call for Chapters (WILEY Publishers) Software Defined Mobile Networks (SDMN): Beyond LTE Network Architecture
4. ^ Abolhasan, Mehran; Lipman, Justin; Ni, Wei; Hagelstein, Brett (2015). "Software-defined wireless networking: Centralized, distributed, or hybrid?". IEEE Network. 29 (4): 32–38\. doi:10.1109/MNET.2015.7166188.