Small Cells and Enterprise Infrastructure Access (Part 1: Setting up the problem)

January 10, 2013

Many enterprise IT departments can provide resources that will enable small cell economics to be more favorable to both the mobile operator and the enterprise. The sharing of select enterprise resources can result in the quid pro quo of lower ongoing costs, enabling small cell based coverage and capacity delivered inside targeted office buildings.

This blog series assumes some familiarity with IP Network technology, and is targeted at product managers and enterprise consumers to shed some light on the opportunities. They intend to cover the issues that are relevant to both the enterprise and mobile operator. As an enterprise IT guy, I will go a little deeper on the set of tradeoffs operationally and financially that each enterprise must evaluate in the context of their environment and policies.

  1. Operations and Service Level Agreements
  2. Rack space, power, and physical access
  3. Embedded cable plant inside the building
  4. Ethernet Network
  5. Firewall
  6. Internet connection
  7. Financial Models

We’ll conclude this first entry in the series with a basic introduction to SpiderCloud Wireless’ technology. The context below is not all the details, but is a brief introduction to the architecture, and it’s fit with enterprise technology and the mobile operator core.

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  • The Radio Nodes deliver one or more radio planes of 3G, LTE, and Wi-Fi into a coverage area similar to a standard Wi-Fi only AP. It is a secured Ethernet attached device that connects via Cat5e or Cat 6 cabling and leverages Power over Ethernet (PoE/PoE+) provided by an Ethernet switch or inline injector.
  • The Services Node is the brain behind the cloud of Radio Nodes installed in the building. It is also a secured Ethernet attached device that coordinates all the Radio Node in-building activity and sends any communications to the mobile core over a single connection.
  • luh Gateway is the termination point at the edge of the mobile operator’s core network, and SpiderCloud’s Service Node is interoperable with many vendors luh implementations.
  • Communications between SpiderCloud’s Radio Nodes, Service Node and the luh gateway are all based on standard IP using tamper proof technologies and IPSec to protect the security and privacy of the mobile operator’s customers.

Stay tuned for the rest of the series!

As a former Enterprise Infrastructure Architect (Mobility/Collaboration at Nike, Inc.), the opportunities for mobile operators to help address enterprise BYOD and mobility challenges for enterprise IT departments are there. Opportunities to cultivate value-added services beyond coverage and capacity in the Enterprise space are built upon strong customer relationships and a proven technical foundation. Positive mindshare and perceptions in the eyes of the enterprise buyers will create invitations to future opportunities.

A new and more important role is emerging for mobile operators where enterprise mobility and value-added IP services is part of the ‘package.’ Mobile is the heartbeat of any organization, and wireless is the digital oxygen that our devices breathe at home and on the road.

Art King, SpiderCloud Wireless, Director of Enterprise Services & Technologies

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Part 5 of 5: Why “Local data switching” is of the utmost importance for scalable small cell deployments

July 21, 2011

A unique attribute of SpiderCloud Wireless’ SmartCloud® system is the ability to provide local data switching and IP session continuity while fully integrated with user mobility. Local data switching allows enterprise subscribers to directly access the corporate Intranet. It also offloads a mobile operator’s backhaul requirements and reduces traffic load on mobile core elements allowing for faster user experience, new services and applications.

Next generation femtocell products will have the capability to support local traffic offload through the support of LIPA (Local IP Access). LIPA allows an IP-enabled UE to access the enterprise network through a local IP address, in addition to the operator assigned IP address. However, when a “cluster” of stand-alone femtocells are deployed to provide coverage across an enterprise, they fail to provide IP address continuity for local data access, which makes LIPA impractical in a mobile environment as shown in the example of figure 1.

SpiderCloud Wireless’ centralized architecture supports IP address continuity and ensures that mobility events across radio nodes do not impact the assigned IP address. The entire Enterprise RAN (E-RAN) represents a single point of touch to LIPA services and a single IP address is used independent of the serving SCRN. Centralized cluster management and enforcement means local switching policies don’t have to be provisioned for each and every individual SCRN – greatly reducing administrative burden on the operator.

The SmartCloud system has been designed to provide maximum flexibility and to support configurable data switching modes such as ‘tunnel mode’ where the SCSN passes all the UE traffic to the core or ‘local-switch mode’ where the UE is assigned a local IP address, its traffic is forwarded to the local network and access control lists can be provisioned to support various tiers of enterprise subscribers.

A big benefit of this scalable architecture is that the complete session history and details are aggregated at the SCSN and node-to-node mobility does not create disparate records for the same session. Session details such as call duration, bandwidth consumption, session source and destination, performance statistics, etc. are available locally. A single call data record can be generated by the SCSN that includes locally switched traffic volumes for all SCRNs the user associated with, through the life of the PDP context in the enterprise, along with detailed handover history. The mobile operator has access to call detail records (CDR) for authorized users, guest users or both while CDRs for non-LIPA connections remain unaffected and continue to be created by the operator’s core network elements allowing for differentiated billing.

To summarize the 5-part blog series: The SmartCloud architecture is a purpose-built Enterprise Radio Access Network (E-RAN) and the only system currently available that can scale to 3G network demands when deployed inside an enterprise environment.

  • The centralized RF and topology management algorithms optimize coverage and reduce the cost of deployment of an indoor cellular network
  • Centralized mobility management combined with soft handover allows the system to scale to support large numbers of data-hungry HSPA subscribers
  • Conditional access along with admission control and QoS policy enforcement allows dynamic and multi-tiered hybrid access offering the flexibility for preferential and secure services to various tiers of enterprise subscribers while providing basic connectivity to guest users
  • Local data switching helps offload the macro network and the operator core offering better user experience and IP address continuity during mobility events
  • The E-RAN architecture exposes a single management interface to the operator, facilitating provisioning and network management functions and resulting in a reliable and scalable system

The E-RAN system can scale to meet the requirements of the network operator for deployment within licensed spectrum by providing a secure control point that can be flexibly administered while meeting the needs of demanding IT managers within the enterprise.

Tassos Michail
Director of Product Management

Part 4 of 5: Soft handover – a mobility “must”

July 21, 2011

Soft handover is a key feature of any mobile network and a “must have” for any sort of deployment – outside as well as inside. SpiderCloud Wireless’ centralized E-RAN architecture makes it possible to support soft handover between radio nodes inside an enterprise. Indeed – E-RAN system handover algorithms have been designed and optimized to improve coverage and system capacity and reduce interference effects.

Soft handover (SHO) as a concept is commonly referred to as “make-before-break”. When a UE (device) is in a session, i.e. when it is connected to one of the cells in the network (the serving cell) and moves to the coverage area of another cell, radio links first get setup on the cell that the UE is moving towards and then deleted from the cell that the UE is moving away from. This helps improve the stability of the session serving the UE. When a UE is in session, but in the coverage area of two adjacent cells, the UE may be concurrently connected to both cells. In this case both cells are said to be in the active set of the UE. The spatial separation of two radio links results in a higher reliability of the connection to the UE with a lower level of interference to the system.

Hard handover (HHO) on the other hand follows the concept of “break-before-make”. A system using hard handover forces a UE to move to a new cell whenever it determines the new cell to be better than the serving cell. To do this the UE has to tear down any active connections and then start a session on the new cell. Due to the fact that session continuity cannot be maintained, most systems implement a HHO hysteresis threshold in order to avoid frequent handovers of UEs located near the cell edge (ping pong effect). As a result, most of the times HHO causes the UE to drag the cell longer which can cause interference and capacity issues to the system. Moreover, lack of soft handover requires a greater degree of cell overlap which for an enterprise deployment implies additional cells or higher capital expenditures. SpiderCloud Wireless’ E-RAN system supports both soft and hard handover. SHO is used when a UE is moving between the coverage areas of the enterprise cells. HHO is used only between enterprise cells and the macro network. With macro handover, cell dragging is not as big of an issue as the macro nodes transmit much higher energy compared to the indoor nodes. On the other hand, in the enterprise network all cells are roughly equally powerful and cell dragging can rapidly cause massive issues as few users can consume most of the Rise-over-Thermal (RoT) budget of a cell.

Soft handover improves cell coverage and boosts network capacity

In multi-cell deployments users expect to get the same level of performance most of the time, regardless of location and distance from the nearest cell. Due to the nature of the wireless channel, shadowing and fading effects result in signal fluctuation which can cause loss of connectivity if the system is not designed with sufficient fade margins. This scenario is aggravated near the cell edges as the propagation loss increases. In order to overcome this, most systems are designed with sufficient fade margin so they can achieve at least the performance of “un-shadowed” propagation all but a fraction of the time, known as the outage probability. In addition to coverage improvements, SHO helps reduce interference and increase capacity of the network. UEs in soft handover operate at the lowest possible transmitted power as the uplink is always power controlled from that cell in the active set with the lowest path loss. Due to the high user density, medium to large enterprise deployments can greatly benefit from SHO as the number of users expected to be in SHO at any time can be anywhere between 20% to 50% at any given time.

As data usage in 3G cellular networks grows rapidly, the lack of SHO quickly becomes a system bottleneck within an enterprise indoor wireless system. A system without SHO support would have to force these users to back off their power to prevent interference overload and this would have a direct effect on their HSUPA throughput performance. In fact, a 3 dB back off in power will cause a 50% reduction in throughput for a system without SHO. In a system with SHO support, interference management techniques can be applied directly to the user causing the largest interference in the system. This will result in more balanced throughputs across all the users in the system as well as a higher aggregate system throughput.

In an enterprise network where the performance requirements entail a very high rate of handover success and less than 1% call blocking probability, a deployment of stand-alone femtocells without SHO will not scale to support hundreds of subscribers within a building or a floor that consume 3Gb per month or more. It is impractical to manage and troubleshoot any deployment of more than 4 to 5 Femto Access Points even if SHO for stand-alone femtocell were technically feasible, in the absence of a premises based controller architecture.

Soft handover improves voice traffic performance

Last but not least, soft handover helps improve voice call quality. As a large fraction of users in the enterprise may be in soft handover at any time, call robustness increases without the need to increase cell overlap and interference into the macro network. On the contrary, in an enterprise deployment of stand-alone femtocells with HHO only, the average voice break per handover can be as much as 100ms (due to signaling and transfer of context requirements).

In the next blog we’ll address why the importance of true ‘local switching’ and the trending towards centralized on-premises control of small cells.

Tassos Michail
Director of Product Management

Part 3 of 5: The importance of Centralized Mobility Management for Scalable Small Cell Deployment Within the Enterprise

July 21, 2011

A key differentiator of the SpiderCloud Wireless system architecture is that it enables the network within the enterprise to be considered as a single entity and provides the advantages of reduced traffic load to the core for both control and user plane traffic, with its local switching features. This is particularly important in the context of mobility signaling as it relieves the core from control plane traffic and improves handover latency without unnecessary complexity on the radio node implementation.

In a network without a centralized coordination of mobility events, each handover instance would require a control message exchange between the serving and the target base station. In a stand-alone femtocell implementation, each Femto AP (FAP) is essentially a separate RNC and the serving RNC is the user plane termination endpoint between the access point and the core. As devices (UE) move around the enterprise, each handover is equivalent to an inter-RNC move, requiring RANAP relocation. Therefore a FAP would have to notify the core upon every handover which may only be feasible in very small deployments with a limited number of sessions – but would contribute to significant signaling load as an enterprise network scales to meet user demand.

Example: In an enterprise with six deployed FAPs, the frequency of handovers is estimated to be approximately one per ten seconds where each handover event generates an estimated 2 Kbytes of control message exchange. In medium and large enterprise deployments with more than a handful of small cell radios, the core network would have to cope with a large amount of simultaneous sessions and signaling traffic due to mobility events which could cause the system not to be able to complete handovers in a timely fashion, and thus eventually experience severely degraded network performance.

“Without centralized coordination of mobility events, each handover
requires excessive inter Femto AP signaling which creates
a bottleneck situation at the operator’s core gateway.”

While a stand-alone femtocell implementation could partially alleviate the problem by designating a FAP as the mobility anchor point for the entire “cluster” of FAPs, such an architecture would suffer from significant scalability issues; the system would be vulnerable to over-subscription on the anchor point in question based on-random initial association of UEs-to-FAPs. All traffic between a device and the core would have to be routed through the anchor FAP which would then forward it to the serving access point. The anchor FAP is vulnerable to overload and can become a system bottle-neck. This issue is exacerbated by what is also called the “Front Door Problem”, which occurs when subscribers initially associate with the radio node closest to the front-door. As the FAP becomes the anchor point back to the core and for IP connectivity, all control and user plane traffic must be tunneled back to this single FAP. This poses a scaling problem at the FAP and requires that all FAPs be over-engineered to operate as an anchor point in case they need to carry a large multiple of their own air interface capacity.

SpiderCloud Wireless’ controller-based architecture (where a Services Node can control a large number of Radio Nodes) addresses these issues as the Services Node (SCSN) acts as the only interface with the mobile core network, eliminating the gateway bottleneck issues faced by stand-alone FAP deployments. All mobility events and signaling traffic are centrally coordinated and executed at the SCSN. Mobile devices can perform soft handover between Radio Nodes (SCRNs) with only an active set update procedure as the user plane is always anchored at the SCSN. This approach diminishes mobility control plane traffic to the core, improves bearer handling efficiencies and eliminates bottle-neck points at the SCRN level.

Figure 1: The SCSN acts as the only interface with the mobile core network

As a result, the E-RAN benefits the operator’s core in many ways:

  • Reduced signaling load on mobile core network (estimated 2 Kbytes per handover event)
  • Reduced number of IPSec Tunnels on the core network interface (only one IPSec tunnel is required which reduces the state and scaling requirements on the core gateways)
  • Reduced inter-SCRN handover latency
  • No additional complexity or CPU power requirements on the SCRN (no need for an anchor SCRN)

Centralized mobility management combined with soft handover allows the system to scale to support large numbers of data-hungry HSPA subscribers with usage profiles that exceed 5GB per subscriber per month – which is where the industry is headed.

In the next blog we’ll address why Soft handover is a fundamental must-have feature for any scalable deployment of small cell technologies.

Tassos Michail
Director of Product Management

Part 2 of 5: Mobile Network transformation with a Scalable Enterprise RAN (E-RAN)

July 21, 2011

SpiderCloud Wireless’ E-RAN architecture is designed to meet scalability requirements of small cell technologies when deployed inside a medium to large enterprise. So how is this different than current in-building wireless technologies? The E-RAN system is comprised of the SmartCloud Services Node (SCSN) which centrally controls a number of SmartCloud Radio Nodes (SCRN) deployed throughout the enterprise. The SCSN provides traffic aggregation and session management for all mobile sessions delivered through the radio nodes over the enterprise LAN (nodes powered over Ethernet). It is responsible for access control, radio node management, auto configuration, self-optimization, interference management, local data offload, soft-handover, and core network integration functions. Technical advantages over stand-alone femtocells include:

  • Centralized provisioning, security and QoS policy enforcement
  • Mobility management with soft-handover support
  • Centralized control of the RF environment and topology management
  • Conditional access and admission control
  • Enterprise local traffic offload with mobility

Let’s take a look at why centralized architecture and provisioning is important.

A group of stand-alone femtocells (or FAP) in an enterprise is not a solution that can scale without significant issues and is unlikely to be fit for purpose. Each FAP functions independently of the others and needs to be provisioned, configured and managed separately through the operator core (figure 1) which will naturally lead mobile operators to define clusters of access points adding complexity and cost to the deployment. This leads to a provisioning nightmare for IT managers and operators due to the limitations of current FAPs being deployed inside the enterprise where each FAP has a limit of 4-10 subscribers. This means that only 4-10 subscribers have access to all FAPs or each individual FAP is assigned to a certain group of people based on location. The provisioning limitations limit the FAP to small business customers only. In addition to the provisioning, management and scalability challenges, such architecture raises significant QoS issues. With each FAP having a separate connection to the core, the operators do not have full control of the backhaul quality for the delivery of voice and data services for indoor subscribers, as it is now part of the enterprise Intranet. Moreover this architecture poses security concerns to the enterprise IT, due to the need for multiple operator-controlled IPSec tunnels deep into the enterprise network infrastructure.

Figure 1: In stand-alone femtocell deployments each FAP needs to be provisioned, configured and managed separately – with a limit of 4-10 subscribers per FAP.

SpiderCloud Wireless’ E-RAN system is designed to provide a scalable solution without such complexity by inherently defining enterprise E-RANs through its system architecture. The E-RAN architecture allows a complex collection of SCRNs to be associated with a single SCSN and be presented to the core network as a single “touch point” in terms of control and data plane. This facilitates provisioning and network management functions and results in a reliable and scalable system.

Some of the benefits of centralized architecture include:

  • Access control list for the enterprise is maintained and enforced centrally at the SCSN
  • There is no need to individually administer and provision every individual SCRN and more importantly each SCRN is not required to maintain user white lists that may exceed its VLR limitations
  • Centralized management of events, alarms and performance monitoring
  • Service and QoS policies for the enterprise are maintained and enforced centrally at the SCSN
  • QoS can be extended over the backhaul to the core network by marking egress traffic to prioritize voice
  • Simplified security configuration (single IPSec tunnel ) reduces the risk of unauthorized access to the enterprise infrastructure

Figure 2: SCSN presents entire cluster as a single management point

While a stand-alone femtocell implementation could possibly be integrated with a network management system to partially address the centralized provisioning limitation, such an approach comes with complexity and added cost on the FAP implementation. With all these elements functionally implemented on the SCSN, SpiderCloud Wireless’ E-RAN system is a more reliable and scalable on-premises solution for 3G coverage and capacity.

In our next blog we’ll address ‘Mobility management with soft-handover support.’

Tassos Michail
Director of Product Management