Staggered quadrature phase-shift keying (SQPSK), also known as offset quadrature phase-shift keying (OQPSK), is a method of phase-shift keying (PSK) in which the signal carrier-wave phase transition is always 90 degrees or 1/4 cycle at a time... (Continued)

Looking for something else?

Staggered quadrature phase-shift keying (SQPSK), also known as offset quadrature phase-shift keying (OQPSK), is a method of phase-shift keying (PSK) in which the signal carrier-wave phase transition is always 90 degrees or 1/4 cycle at a time. A phase shift of 90 degrees is known as phase quadrature.

In SQPSK, the data is placed alternately on two channels or streams called the I channel (for "in phase") and the Q channel ("phase quadrature"). A single phase transition can never exceed 90 degrees. This property contrasts SQPSK with conventional quadrature phase-shift keying (QPSK), in which the phase can sometimes change by 180 degrees (two 90-degree shifts in a single transition). The average magnitude of the phase transitions is smaller with SQPSK than with conventional QPSK. The result of the smaller average phase "jump" is an improved signal-to-noise ratio (SNR) and a reduced error rate.

SQPSK and QPSK are not the only methods of PSK in common use. In binary phase-shift keying (BPSK) there are two possible states for the signal phase: 0 and 180 degrees. In QPSK and SQPSK there are four possible states: 0, +90, -90 and 180 degrees. In multiple phase-shift keying (MPSK) there can be more than four possible states for the signal phase. An example is the use of eight phase states: 0, +45, -45, +90, -90, +135, -135 and 180 degrees. More than eight phase states are rarely used because that takes the signal complexity past the point of diminishing returns and the error rate actually increases.

This was first published in June 2007

Content

Find more PRO+ content and other member only offers, here.

Oldest

SearchSDN

• ICYMI: Masergy expands cloud marketplace with Microsoft Azure

Masergy has added the Microsoft Azure cloud platform to its cloud marketplace, while Sonus demonstrated that its SDN controller ...

• VMware NSX sales a positive sign for SDN market

VMware has reported growing NSX sales, the latest indicator that the SDN market has momentum. Rival Cisco has also reported ...

This week, experts discuss software-defined WANs as an alternative to traditional wide area networks. And one startup is looking ...

SearchEnterpriseWAN

• Cloud-managed networking makes VPN a snap

Provisioning and deploying a WAN and VPN is an everyday function for engineers. But can you do that for an office 4,000 miles ...

• Three new takes on WAN optimization

Once considered new technology, WAN optimization is now widespread, and enterprises are including it in their networks from the ...

• 8 steps to a successful MPLS migration

Successful MPLS migration takes careful consideration. Robert Sturt offers some advice about the steps you should consider before...

SearchUnifiedCommunications

• UC blogs: Building on your enterprise mobility strategy

In UC blogs this week, analysts discuss how a mobile center of excellence can support an enterprise mobility strategy and how ...

• WebRTC security concerns shouldn't deter enterprises

Native media encryption and regular Web browser updates mitigate WebRTC security threats. Authorization and fraud-prevention ...

• Office 365 telephony an emerging threat to Cisco UCM

Microsoft is building out Office 365 telephony, a strategy that could trump Cisco in providing an all-in-one communications suite.

SearchMobileComputing

• How 2-in-1 tablets fit into the enterprise

Enterprise users who want to be freed from their PC but maintain that functionality can turn to the burgeoning 2-in-1 market.

Developing mobile apps can be costly. MADPs ease the burden by giving developers everything they need to build apps in one place.

• EFSS combats consumer cloud storage risks

Companies wrestle with the security concern of using consumer cloud storage, but there are enterprise file sync-and-share options...

SearchDataCenter

• New data center tools manage 'epidemic of disorganization'

There are ways to combine DCIM and ITSM systems in the data center that give even better visibility.

• Enterprise data security best practices mean IT teamwork

Data center managers take on the burden of protecting the business's data assets. Discover the best strategies to deploy ...

• Uptime certification misuse leads to big changes

The Uptime Institute's tier-level certification will now only be handed out to constructed projects that meet the standards, not ...

SearchITChannel

• Managed services business model relies on careful client acquisitions

When it comes to customer acquisitions, MSPs have to be particularly selective. Learn best practices to steer clear of bad ...

• Inside a DaaS service pact: EarthLink teams with IndependenceIT

EarthLink, a cloud service provider, and IndependenceIT, a DaaS vendor, provide an example of partnering in the emerging hosted ...

• Cisco ends SSD hardware production

Cisco has dropped its Invicta all-flash product line, leaving customers to buy SSD hardware for its UCS servers from third ...

Close