VoIP Quality and Reliability: Ensuring Call Quality for Your Business

The Four Factors Affecting VoIP Call Quality

Factor 1: VoIP Latency (Delay)

VoIP Latency is the time it takes voice data to travel from speaker to listener. High latency causes noticeable delay: you speak, then wait for the other person to hear you, then wait for their reply. This awkward delay ruins conversation flow.

Acceptable VoIP Latency: under 150ms (150 thousandths of a second). At 150ms, the delay is barely noticeable. Above 300ms, the delay becomes very apparent, and conversations feel unnatural.

How VoIP Latency happens: voice is digitised, sent through your broadband, travels through your ISP’s network, through the internet backbone, through the VoIP provider’s network, to the destination. Each hop adds milliseconds. Total: typically 20-100ms under normal conditions.

Your ISP and broadband quality determine most of the VoIP Latency. Broadband with poor routing might add 100+ ms. Leased lines and well-provisioned broadband add 20-50ms.

Factor 2: VoIP Jitter (Latency Variance)

VoIP Jitter is the inconsistency in VoIP latency. If latency is consistently 50ms, VoIP systems adapt, and quality is fine. But if VoIP latency varies from 50ms to 150ms to 30ms to 100ms (VoIP jitter), voice packets arrive inconsistently and reassembling them into coherent speech becomes problematic.

Acceptable VoIP jitter: under 20ms variance. Above 50ms jitter, voice quality degrades noticeably (robotic sound, gaps, echoes).

How VoIP jitter happens: if broadband is congested, some packets are delayed more than others. Network routers prioritise differently. Equipment has variable processing times. Result: variable latency.

Good broadband has minimal jitter. During congestion, jitter spikes. This is why broadband quality matters for VoIP.

Factor 3: Packet Loss

VoIP encodes voice into packets. If a packet is lost (dropped by a router, dropped due to congestion, or never arrives), that audio gets lost. A small amount of loss is tolerable. Large amounts degrade the quality severely.

Acceptable packet loss: under 1%. Above 3%, quality becomes significantly impaired.

How packet loss happens: routers have limited buffers. When congested, they drop packets. Some network paths are unreliable. Wifi coverage is spotty. Occasional packet loss is normal. Persistent packet loss indicates network problems.

Your broadband provider’s network quality determines packet loss. Enterprise broadband has near-zero loss. Consumer broadband might have 0.5-2% loss during peak congestion.

Factor 4: Bandwidth Availability

VoIP latency requires minimum bandwidth per call. Too little bandwidth and voice quality drops (codec is forced to compress more heavily, audio becomes low-quality). Competing traffic (file downloads, cloud syncing) can starve VoIP of bandwidth.

Requirement: 0.1 Mbps per active call for high-quality codecs. 0.05 Mbps per call for compressed codecs (lower quality but more efficient).

Example: a business with 10 staff, where typically 3-4 are on calls simultaneously, needs 0.3-0.4 Mbps minimum for VoIP. Other business activity (email, web, cloud) needs 2-5 Mbps. Total: 2.5-5+ Mbps to support VoIP plus other traffic comfortably.

Quality of Service (QoS): Prioritising VoIP Traffic

VoIP call quality is sensitive to network congestion. When broadband is saturated with other traffic, VoIP suffers. Solution: Quality of Service (QoS) configuration.

QoS prioritises VoIP traffic ahead of other traffic. When broadband is congested, VoIP packets are prioritised. Lower-priority traffic (large file downloads, streaming video) is throttled.

How QoS Works

Your router is configured to identify VoIP traffic (by port numbers or device addresses). VoIP traffic is tagged as high-priority. When congestion occurs, high-priority traffic gets through first. Lower-priority traffic waits.

Result: VoIP continues working even when broadband is congested. File downloads might slow down, but your call continues uninterrupted.

Implementing QoS

QoS is configured on your router. Most business routers support QoS. Configuration requires identifying VoIP devices and traffic, setting priority levels, and testing to ensure VoIP is protected.

Many VoIP providers provide QoS configuration guides for common routers. If your router doesn’t support QoS, upgrading the router is a smart investment.

Broadband Quality Tiers and VoIP Implications

Consumer Broadband

Typical: 50-100 Mbps. Latency: 50-100ms. Jitter: 10-50ms during peak hours. Packet loss: 0.5-2% occasionally during congestion. No SLA.

VoIP performance: adequate for most uses, but occasional quality issues during peak hours. Calls might sound slightly delayed or have brief audio drops.

Cost: 30-60 pounds/month.

Business Broadband

Typical: 50-150 Mbps. Latency: 30-50ms. Jitter: 5-15ms even during peak hours. Packet loss: less than 0.1% under normal conditions. SLA: 99-99.5% uptime.

VoIP performance: professional quality. Calls are clear and responsive. No noticeable delay. Minimal audio issues.

Cost: 50-150 pounds/month.

Leased Line (10-20 Mbps)

Typical: guaranteed 10-20 Mbps. Latency: 10-20ms consistently. Jitter: 1-3ms. Packet loss: near-zero. SLA: 99.9% uptime with service credits.

VoIP performance: excellent. Calls are crystal clear, zero delay, professional quality even under heavy load. Best possible experience.

Cost: 400-600 pounds/month.

Recommendation

For most businesses, business broadband is adequate for professional VoIP quality. Consumer broadband works but might have occasional issues. Leased lines ensure best performance and are worth considering for businesses where call quality is critical (sales, customer service, support).

Network Setup for Optimal VoIP Quality

Beyond broadband speed, network configuration affects VoIP quality:

Use Wired Ethernet for VoIP Phones

Wifi is convenient but introduces variability (signal fluctuation, interference, range limitations). Desk phones should connect via Ethernet cable to your network. This eliminates wifi variability and ensures consistent quality.

Remote workers using softphones might rely on wifi. Encourage them to use wired connection when possible, or ensure their wifi is strong and reliable.

Separate VoIP from Other Traffic (Optional)

For maximum reliability, some businesses create separate network VLANs (Virtual LANs) for VoIP traffic. VoIP gets its own network segment and never competes with file downloads or video streaming.

This is nice-to-have but not essential if QoS is properly configured.

Backup Connectivity

If your broadband fails, VoIP fails. Backup connectivity (second broadband line, 4G mobile backup) keeps your phones working even if primary broadband fails.

For critical businesses, hybrid connectivity (leased line primary + broadband backup) is ideal. If primary fails, calls automatically route over backup.

Monitor Your Network Quality

VoIP quality depends on network health. Monitor latency, jitter, and packet loss regularly. Most VoIP systems provide quality reports showing these metrics.

If you notice quality degradation, diagnose the cause: is broadband congested? Are there connectivity issues? Is nearby interference affecting wifi? Proactive monitoring catches problems before they impact calls.

Advanced VoIP Quality Optimization

For businesses with critical communication needs, advanced optimization techniques improve quality further:

Codec Selection

VoIP uses audio codecs (compression algorithms) to encode voice. Different codecs offer different quality/bandwidth tradeoffs. High-quality codecs (G.722, Opus) provide excellent clarity but need more bandwidth. Compressed codecs (G.729) save bandwidth but reduce quality. Your VoIP system typically negotiates the best codec both parties support. Understanding this helps troubleshoot quality issues.

Echo Cancellation

VoIP systems include echo cancellation to prevent callers hearing themselves. Poor echo cancellation creates annoying feedback. Good VoIP systems have sophisticated echo cancellation. If you hear echo, it’s usually a sign of network issues (delay allowing echo to be perceived) rather than PBX problems.

Jitter Buffers

VoIP systems use jitter buffers to smooth variable-latency packet arrival. Packets arrive inconsistently, jitter buffer stores them temporarily, then releases them at consistent rate for smooth audio. Too-small buffer causes audio drop if packets arrive later than expected. Too-large buffer adds delay. VoIP systems auto-tune jitter buffer size based on observed jitter.

Before migrating to VoIP, ensure your broadband is adequate:

Step 1: Assess Call Volume

How many simultaneous calls do you typically have? During peak hours? This determines minimum bandwidth needed for VoIP.

Step 2: Test Current Broadband Quality

Run latency, jitter, and packet loss tests. Many online tools provide this (speedtest.net shows some metrics). If quality is poor, upgrade broadband before migrating to VoIP.

Step 3: Choose Appropriate Broadband Tier

For most businesses, business broadband (50-100 Mbps) is adequate. For businesses with heavy call volume or critical call requirements, leased line is worth considering.

Step 4: Configure QoS

Once you have broadband and VoIP system, configure QoS to prioritize VoIP traffic. This ensures VoIP quality remains high even when broadband is busy.

What Multidata Recommends

VoIP quality depends on broadband quality. If you want professional-grade call quality, invest in quality business broadband or leased line connectivity. Don’t cheap out on broadband and then expect excellent VoIP quality. The two are inseparable.

Before migrating to business VoIP, assess your current broadband quality. If it’s poor, fix broadband first. If it’s adequate, configure QoS and deploy VoIP with confidence that call quality will be professional.

Contact Multidata to assess your broadband quality for VoIP readiness. We can test your current connectivity, identify any bottlenecks, recommend broadband upgrades if needed, and help configure QoS settings. We’ll ensure your VoIP deployment has professional-grade call quality from day one.

For technical specifications on VoIP standards and quality metrics, Ofcom publishes guidance on VoIP services and quality standards in the UK.