One of the challenges in mobile computing is battery life. It's hard to be productive with a dead battery, so IT personnel and users alike need to think about maximizing run time between charges.

Optimizing the power conservation settings of a mobile computer or communicator, including dimming the display when on battery, turning off the display and hard drive after a pre-set period of time, suspending (keeping memory alive but the computer otherwise powered down) and hibernating (writing the image of main memory to disk for later resumption) help in getting the most out of any given charge. (Read a related story on how to get the most out of your battery.)

And there are also power conservation settings in most Wi-Fi adapters that (at first glance, anyway) are intended to allow a high degree of control over the power consumed by the wireless network interface card (NIC) found in almost all notebooks and many handhelds as well. In gross terms, wireless power conservation involves turning off the radio, synchronously or asynchronously with the fixed infrastructure, for a portion of time - a technique used in various forms on essentially all production wireless systems today, including WANs. But this technique motivates an interesting and fundamental question: do Wi-Fi power-conservation techniques, when enabled, actually save a meaningful amount of energy or have any negative impact on throughput?

We set out to define a simple test to answer these questions as they pertain to 802.11's Power Save Mode (PSM), the most common form of Wi-Fi power saving implemented today. We do note that there are several new power saving mechanisms defined for 802.11n (see related story on standards) gear, but we have not found those to be widely implemented, so we could not assess those at this juncture.

Vendors have delivered a number of PSM variants, with the primary difference being how quickly and how often the adapter wakes up. Having a NIC wake up faster could negatively affect power consumption, the fundamental tradeoff in this strategy, although this could theoretically improve throughput. The opposite of PSM is Constantly Awake Mode (CAM), in which PSM is disabled. Our test compared various forms and implementations of PSM against CAM and, for good measure, a wired gigabit Ethernet baseline test.

Whitepapers

• Best Practices for HP Servers and HP Enterprise Virtual Array in a Microsoft Exchange
• Compliance, Protection, Recovery: A Layered Approach to Laptop Security
• Endpoint Security: Data Protection for IT, Freedom for Laptop Users
• IT Departments on Data Security: A Research Concepts Survey
• Laptop Security Tool Helps Allina Hospitals Track 97% of IT Assets
• The Case for an Untethered Enterprise

View more WIRELESS & MOBILE whitepapers

Webcasts

• Key Considerations for a Successful 802.11n Deployment
• The High-Touch Remote Helpdesk: Centralized Support for the Decentralized Organization
• From Wired to Wireless with Confidence - On Demand
• High Availability for SQL Server 2005 Using Array-Based Replication and Host-Based Mirroring Technologies
• Technical Overview of Exchange Server 2007 with HP Servers and Storage
• Bringing Order and Security to your Mobile Workforce: Corporate Mobility Policy and Device Management On-Demand

View more WIRELESS & MOBILE webcasts

Special Reports

• Learn how to Keep your Mobile Workforce Connected
• The Wireless Explosion

View more WIRELESS & MOBILE special reports