Morning, ladies and gentlemen. On behalf of Comba Telecom Systems Holdings Limited, I would like to welcome all of you joining the 2022 interim results investor presentation video conference. In today's meeting, there will be a presentation followed by Q&A section. If you wish to ask questions during the Q&A section, please click on the Raise Hand button and wait for further guidance from us. Today we have four senior management joining us from Hong Kong and Guangzhou. From Hong Kong, may I introduce first the Chairman, Mr. Fok Tung Ling. The Executive Director and group CFO, Mr. Ken Chang. And from Guangzhou, may I introduce the Executive Director and President of the group, Mr. Xu Huijun. And the Executive Director and Senior Vice President of the group, Ms. Huo Xinru.
Now, may I invite Mr. Chang Fei Fu, Executive Director and Group CFO, to present the financial highlights for the first half of 2022. Mr. Chang, please.
Thank you. Good morning, everyone, and welcome to Comba's interim results section. Today I'm going to provide an overview first on the financial section. Overall, in the first half of this year, we have a big rebound from what we have seen in terms of revenue, in terms of the bottom line since last year. The first half of 2022, revenue is HKD 3.04 billion, which is up 25.8% year-on-year. Thanks to the recovery on the antenna business, which roughly represent half of our business. Gross profit is HKD 847 million, which is up 24.4%. Gross profit margin, which is 27.8%, slightly down by 0.4% from the same period of last year.
In fact, our product margin actually has been stable, even has gone up. On relative terms, the service margin has come down slightly that somehow diluted the overall gross profit margin. Operating expenses is HKD 745 million, which is down by 1.1%. Later I will talk about our OpEx ratio, which actually has come down substantially. Profit before tax is HKD 82 million, which turn around from the losses from last year. Income tax, HKD 23 million. The profit attributable to shareholders is HKD 90.38 million, which has a big turnaround from losses from last year. Net profit margin is 3%. Basic profit per share is HKD 0.0325. This year we resumed the dividend.
Dividend per share that we propose to pay out is HKD 0.01 per share, which represents the dividend payout ratio of about 30.8%. Overall, we have a significant reduction in the OpEx ratio. From the same period of last year, which is about 35.9%, we have come down to about 28.7%, which has been quite substantial. Basically, all the categories of the OpEx have come down, particularly on categories like income tax and other expenses, which have come down respectively 13.4% and 22%. The other categories also have seen a pretty significant come down in terms of ratio. This is also thanks to our rigorous expense control that actually we have been implemented over the last few years.
In terms of the financial position, we have a net cash position of HKD 713 million, which is up by 27.5% since last year. Total asset is up slightly by 0.9% to HKD 11.3 billion. Total liability is HKD 7.26 billion, which is up by about 10%. Net asset about HKD 3.7 billion, which come down by 8.6%. The net asset come down because of the non-operating adjustment that we have, we have adjusted, in, the second half of the last year. NAV per share is HKD 1.35.
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Okay, good. In terms of the turnover day, we actually have seen the turnover day for most of the metrics have come down. Inventory turnover day has come down by 27 days to 114 days. Accounts receivable turnover day has come down by 64 days to 248 days. Accounts payable days have come down by 48 days to 371 days. The turnover day also indicate that we are actually in a pretty good operating financial metrics. Cash conversion cycle is slightly negative at nine days, negative nine days. Operating cash flow at positive HKD 95 million, which is a big turnaround of a negative in the same period of last year. The gross gearing ratio has gone up by 1.9% - 14.3%.
Here is because in the first half of the year, we actually transitioned from last year losses to profit. We're also in a position of managing the cash flow and be cautious on our cash position as well as our liability position. I think we are in a pretty good position to lower this ratio in the second half of this year. Debt to asset ratio is 64.2%, gone up slightly by 5.3%. The ROE is 4.8%. Right now, our interest-bearing debt is sitting at about HKD 1.6 billion. We actually has gone up from about HKD 1.4 billion in the same period of last year.
Again, as I mentioned, we're in transitioning of, also paying off some short-term debt, while we witness from the losses to profit. I think we are in a better position in the second half of the year. The net cash position actually is one of the highest period, sitting at about HKD 700 million. I think overall, we are sitting in a pretty good financial position at the moment. Over the last 10 years, our operating cash flow, except one year, has been positive. Basically, nine out of 10 years has been all positive. This year, we're having a good recovery in terms of the net profit as well as the operating cash flow.
Let me demonstrate our revenue by business breakdown. First of all, by customer. China revenue actually has gone up significantly, driven by China Mobile and China Unicom. China Mobile have seen a revenue gone up by 116%, and China Unicom has gone up by 106%. This is because since the middle of last year, the operator has been busy doing the centralized procurement on the passive antenna. We actually have done, we have secured a pretty good market share, and we have done relatively well. On China Telecom, down by about 20%, and China Tower down by about 25%. On the other hand, international business also have seen a healthy growth at about 11.4% growth.
Particularly, we have seen some countries like the European countries, the Middle East, and our international OEM business have seen a pretty good and significant growth over the last half year. Other customer went down by 7.9%, and here is to highlight our one of the major subsidiary, ETL, which is the third largest operator in Laos, which roughly account for 3.1% of our total revenue, is down by 7%. However, the Laos currency, the Laos kip depreciated by about 22% in the same period. In other words, in local currency term, ETL actually has increased in the revenue by roughly about 13%. If we look at our revenue by business breakdown, we actually have seen the antenna business.
The antenna business roughly represent half of our total revenue, went up significantly in the first half of this year. It went up by 123.5% in the first half. In the China market, it actually has gone up by more than 200% year-on-year. On the other hand, the network system has come down by 26.8%. This is because the centralized procurement on the small cell, the execution side actually has been put in the second half the year. The second half of the year, we actually assume the network system will have pretty good meaningful recovery on that term. Service segment went down by about 10% and the wireless transmission business went down by roughly about 5%.
Okay, this is the overview on the financial part. Now I will turn the business and strategy part to Mr. Xu Huijun .
Thank you, Mr. Chang. Now may I invite Mr. Xu Huijun, Executive Director and President of the Group, to present industry development and company outlook. [Foreign language]
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