As Small Cells become closely integrated with the existing macrocellular network, there are many areas of interworking and interoperability to consider. The system grows in complexity as our smartphones are guided between 3G, LTE and Wi-Fi technologies as we move around. We'll also be switched between Macrocells and Small Cells too, yet expect ever-higher data rates and performance and ever-lower cost.
Today's network test platforms can scale to emulate real-world usage from thousands of devices, allowing realistic behaviour to be determined and assessed before deployment. This reduces the risk of deploying ineffective or inefficient systems, and helps operators roll out all aspects of new Small Cell technology faster with a higher degree of confidence that it will achieve superior quality of experience.
A growing level of complexity
A complete HetNet (Heterogeneous Network) combines 2G, 3G and 4G radio technologies and frequency bands, alongside multiple frequency bands. Some people would include Carrier Wi-Fi within that scope.
Other complexities include:
- Many more Small Cell vendors providing equipment
- Much more intelligence at the edge of the network, both in UEs (smartphones) and cellsites
- More automation, including SON (Self-Organising Networks)
- Carrier Wi-Fi, which is being seen by some as "just another Radio Access Network technology"
- HetNet techniques introduced by LTE Advanced, such as CA (Carrier Aggregation) and CoMP (Co-ordinated Multi-Path)
- Network sharing
- A roadmap of new features, both 3GPP standards and proprietary
A limited appetite for risk
There used to be an old saying that "nobody got fired for buying IBM." It reflects a conservative view still present in many telecom operators who don't want to take chances by adopting new techniques or products before they are fully mature and proven. But with data traffic burgeoning and traditional voice revenues declining, we are entering a new competitive era which demands new technology. The leap to LTE is the first step but won't solve the capacity or coverage problem alone. Large numbers of small cells will be needed, which leads to much larger changes in the wider ecosystem and operations teams of network operators.
Fortunately, best practices are evolving which can validate new HetNet strategies and components at scale prior to their deployment or upgrade.
Emulating the network in full
Test platforms now exist which can scale to emulate the live network, up to thousands of individual users (smartphones) and layers of different cellsites (macro/micro/pico/small).
These systems can generate huge amounts of network traffic with varying:
- Services (voice, web surfing, video streaming...)
- Mobility (moving around and handing over between cells)
- Interference (both between end-user devices and Small/Macro Cells)
- Impairments (technical faults, backhaul bottlenecks, outages etc.)
Measuring the results
Live networks have a set of KPIs (Key Performance Indicators) that they measure and report, indicating the health and underlying Quality of Experience (QoE) each user would get. These typically include call drop rates, voice quality and data speed/latency.
A network emulation test would provide a similar set of KPIs, with high confidence that this would match the real world when deployed. Typical KPIs relate to each type of service:
- Voice: MOS (Mean Opinion Score). 4.0 and above is considered good
- Data: It's not just raw speed, but the overall series of data transactions that relate to how quickly a web page or other request is handled. Factors include:
- Transaction Latency, including time to first response
- Transactions per second
- Concurrent transactions
- Uplink and downlink throughput
- Re-transmissions and transaction failures
- Video: Latency, jitter and sustained throughput
Reducing the risk during change
In a complex HetNet of the future, operators will want to validate the impact on their network of any major change. This could range from introducing a new vendor (e.g. Small Cell product) or a new feature (e.g. software upgrade) to new technology (e.g. LTE-Advanced).
We can also expect to see greater automation through SON (Self Organising Networks) that will co-ordinate between multiple vendor equipment types and software versions.
No mobile network is the same. Each has its own combination of vendor products and software versions, differently configured and handling different user traffic patterns. Traditionally, some operators have relied on their main RAN vendor to do all the validation themselves. Growing competitiveness and complexity may make this approach more risky than before.
Aligned with other back-office tools
Network emulation can also be used to debug and/or fine-tune the live system, researching unusual or poor network performance and assessing how configuration changes would affect behaviour. This also works alongside other software tools:
- Theoretical RF planning tools predict results based on assumptions about network performance. These can be configured for new features and optimisations based on test laboratory validation results.
- Live network KPIs reported by Performance Management can be compared with expected results. This provides rapid feedback of configuration and other system changes, increasing the confidence to explore and test system enhancements.
Network emulation test platforms allow operators to validate each new product, feature and configuration in the lab prior to deployment on the live network. They also provide feedback on the likely impact on network configuration changes and issues like interference and scalability.
At the end of the day, operators' test systems and strategies must be as flexible and innovative as the HetNets themselves. When expressed as a fraction of the cost of new RAN hardware and software, they have a strong business case justified by both lower cost (more efficient network/latest technology) and better reputation (fewer outages/poor performance after upgrades).
It is capabilities and tools like this which can accelerate the deployment of Small Cells and HetNets to meet the demand for wireless data capacity seen today.
Our thanks to Joe Zeto, Director, Product Marketing, IXIA, for his insight in writing this article
For further insights, read Ixia's new eBook, Small Cells, Big Challenges: A Definitive Guide to Designing and Deploying HetNets
Ixia is a sponsor of ThinkSmallCell